Chapter 6-Scan Parameters
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This chapter describes the Scan Parameters area of the Exam window and
provides detailed information about each parameter. These selections allow you
to customize your scans and processing in various ways.
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0AS Is~ MRI System Reference Manual T'hoe htlent MqiMt
Scan Parameters Area
6-2
The default location for the Scan Parameters area is on the right side of the
Exam window, as shown in figure 6-1. The Scan Parameters area can be
displayed on either side ofthe Exam window. To change the display location,
refer to the "Displaying the Scan Parameters Area" section in this chapter.
Figure 6-1. The default location for the Scan Parameters area.
This area contains the Slice Stack Moving area, the Basic tab, and the All
tab. The Basic and All tabs are described in this chapter while the Slice Stack Moving area is described in Chapter 5. Refer to Chapter 5, Exam Window
Scanning Functions, for complete Slice Stack Moving area details.
• Basic tab-Contains the 12 default parameters and any parameters that have
been added to the tab.
• All tab -Contains all the parameters in the Oasis MRI system, including the
default parameters listed on the Basic tab.
These tabs are described in the following sections.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
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Scan Parameters 0 Basic Tab
The Basic tab contains the fo llowing 12 default parameters, as shown in figure
6-2:
• FOV
• TR
• TE
• FA
• Thickness
• Interval
• Multi slice
• Freq#
• Phase#
• NSA
• Sync. Stop Watch
• Gating
Sync StopWatch
- f otf IIIIIIII'Fo=ff~====,
Figure 6-2. The 12 default parameters on the Basic tab.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
6-4
This tab also contains any parameters that have been added. To add a parameter
to the Basic tab, follow these steps:
I. Click the All tab and drag the scroll box to the bottom of the scro ll bar to
reveal the Config button, as shown in figure 6-3 .
Click DC Level
Reg1on Cut
W-Width1
W-Levell
Shce Ord A
Shce Ord S
Shce Ord C
Plane Order
Rad1al Stack
L1neJBox
Gwde L1ne
G lntvl
Sync
I H-F
( L-R
( P-A
S-C-A
I off
Line
(Yes ( ON ( ON
Figure 6-3. Adding a parameter to the Basic tab.
Drag scroll box to bo:tom of scroll bar
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: Changes made to the Basic tab apply to all Exam windows, not just the one currently in use.
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Scan Parameters 0 2. Click the Config button. The Config Setting window opens, as shown in
figure 6-4. Parameter check boxes that are selected and unavailable are the
Basic tab default parameters.
Conflg Setting Slice Plane -- -:l
D 2o13o D Sequence D Echo Time Mode D ShimMode D Oblique
FOV TR TE FA
D IR Pulse Thickness Interval Multi slice
D Multi Echo D Multi Acquisition D Mode D Stacks
Freq# Phase#
OK
..,
Figure 6-4. The Config Setting window.
3. C lick to select each parameter check box that you would like to add to the
Basic tab.
4. C lick OK to add the parameter(s) to the Basic tab and close the Config
Setting window.
To remove a parameter from the Basic tab, follow these steps:
I. C lick the All tab and drag the scroll box to the bottom of the scrol l bar to
reveal the Config button.
2. Click d1e Config button. The Config Setting window opens.
3. Click to clear each parameter check box you wish to remove. The check
mark will be removed and the parameter will not be displayed on the Basic
tab.
4. Click OK to remove the parameter(s) from the Basic tab and close the
Config Setting window.
6·5
0AS Is~ MRI System Reference Manual T'MhtJent MqHt
6-6
All Tab
The All tab, pa1tially shown in figure 6-5, displays all of the scan parameters
including the defaul.t parameters. Because there are so many sca11 parameters,
not all of them can be displayed at once in th is small space. Use the scroll bar to
locate the desired set of parameters, or c lick the Overview button (figure 6-5) to
open the ScanParam eterL ist window, which is shown in figure 6-7 and
described in the next section.
Slice Stack M0111ng
Positioning
SltceOrd A ( H-F ?] - ( L-R ~I -P-A
S-C-A -off ~r-Li-.ne--==--....,~J
- [Yes ~J Ellllllli[oN ~I Sync I ON ~I
Others
Rece1ver Cod
Figure 6-5. The All tab.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
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Scan Parameters 0 Scan Parameters Area Buttons
The top of the Scan Parameters area (figure 6-6) contains the following buttons:
Reset
~~Overview
~ ~~ ~ Dynamic scan : time table . ~
... ...
Figure 6-6. The buttons at the top of the Scan Parameters area.
Reset - Resets a ll changed parameters to the previously-saved default values.
Ovea-view-Opens the ScanPara meterList window, as shown in figure 6-7.
All of the various parameters found under the All tab can be viewed and
changed in this convenient window, rather than scrolling through the categories
in the Scan Parameter area. Scanning can a lso be started and scan time can be
monitored in this window.
Figure 6-7. The ScanParameterList window.
Dy na mic scan time table-Opens the Dynamic scan time table window,
which provides a visual display of the execution plan for dynamic scans.
The buttons at the bottom of the Scan Parameters area are used during scanning
and are described in the "START, STOP, and Other Buttons" section in Chapter
5, "Exam Window Scanning Functions."
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0AS Is~ MRI System Reference Manual TIN hUM llb,pet
Note: Refer to the "Launcher Buttons" section of Chapter 3, ''System Overview, " for a detailed description of menu customization for Launcher too/bar buttons.
Changing the Scan Parameters Area Display Location
The Scan Parameters area can be displayed on the right or left side of the Exam
window. To change the display location, use the following procedure:
I. On the System Settings Launcher button menu, click Window Setting (this
command appears if the System Settings Launcher button menu has been
customized). The Window Setting window opens as shown in figure 6-8.
2. Click the Exam Window tab on the Window Setting window.
3. Click the desired graphical representation for the Scan Parameters area
location. Additionally, the Protocol Properties area can be displayed either
graphically or by task name from this tab as well (figures 6-8 and 6-9).
4. Click OK to save your choices and close the Window Setting window. The
changes made take effect when the next Exam window is opened.
Figure 6-8. The Scan Parameters area on left of Exam window, graphical display of task list (Protocol Properties area) selected.
6-8 Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
----------------------------------------6 Scan Parameters 0
··~sc• ..... • -... n•se • . .._n,.• .. "laeiTM • ·,...nne. .!< ·s.e nrSE(t, • ""'*'T1fiiE(M~
• "Sal TI._,SE.10 f) ... fnll. q~s.r. • • ..... Jae · ·s.ennar..s. • ·s.enrser•s.
:..,J ... L .. Iplne ..,JWR:t..-St*lt(t) • "Sal T2iMfSI!X)(t) • "S. T'J" Ge (AOAOf)
04tJ •• 012e •• OUI •• 01_ .... ..... .. ....... Ol'c21 •• OUI · · o.•t ..
-TU
·'---
Figure 6-9. The Scan Parameters area on right of Exam window, task name display of task list {Protocol Properties area) selected.
Scan Parameters Descriptions
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The scan parameters are separated into the following sets of related parameters:
Sequence- ! ncludes parameters related to the scan to be performed, such as
slice plane, sequence type, and acquis ition mode.
Seq . Parameter- Includes parameters related to pulse sequences (TR, TE, and
NSA) and slices (thickness, interval, and number).
Advanced - Includes parameters related to add itional functions, such as phase
direction, presaturation, and bandwidth.
RADAR (RADial Acquisition Regime)- Includes parameters related to the
sampling of K-space in a radial pattern.
Saturation- Includes parameters related to the suppression of specific s ignals,
such as fat, water, and silicone.
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Definition: 30 MRA refers to threedimensional magnetic resonance angiography. A slab refers to a collection of slices to be excited with a single excitation pulse, used in 30 acquisitions.
6. 10
T2WPrep (optionai)-A prepulse that enhances the T2 contrast of the imaging
target. When T2WPrep is appl ied to the BASG sequence, tissue contrast
improves but the SNR drops slightly.
MTC (Magnetization Transfer Contrast) - Includes parameters used to change
the contrast of images by moving magnetization from bound protons to free
protons.
VENC (Velocity ENCoding) - Includes parameters related to the use of phase
information to determine the rate and direction of blood flow.
SSP (Sloped Slab Profile) - lncludes parameters related to a sloped slab used to
suppress blood flow saturation in 3D MRA.
MPG (Motion Probing Gradient)- lnc ludes parameters related to scann ing
with the application of a gradient magnetic field to emphasize proton diffusion.
This is used with Diffusion Weighted Imaging (DWI).
Scan Control- Includes parameters related to the tim ing of contrast-enhanced
scans in various scan modes, such as wait t imes, delays, and contrast agents.
RAPID (Rapid Acquisition through a Parallel Imaging Design)- Includes
parameters related to the reduction of phase encode steps, which reduces scan
time.
Gating- Includes parameters used with ECG-, pulse-, and respiratory-gated
scans.
NAVI (NAVIgator Echo) - lncludes parameters related to Nav igator
acquisitions, which are used to reduce a1tifacts produced in a scan region, such
as the heart, where breathing can change the scan position.
PAPE (PA1tial Phase Encode)- Includes parameters related to PAPE, which
improves temporal resolution whi le maintaining image spatial resolution.
F ilter/PostProcessing-Includes parameters related to improving an image's
visual characteristics, as well as other post-processing selections.
Positioning- Includes parameters related to scan position, such as slice order
and plane order.
Others - Includes parameters fo r receiver coils and morning QA functions.
You can change parameter values by selecting from a list of options or by
clicking the up or down arrows (to change a numerical value in a box). You can
also change numerical values by highlighting the value in the box, typing the
new value, and then pressing the ENTER key. Parameters that have a grayed
out appearance are unavailable; th is occurrence depends on the combination
of parameters that have been selected. The Reset button at the top of the Scan
Parameters area resets all parameters to their previously saved default values.
The parameters are described in the remainder of this chapter.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: The values that can be set may be limited by the Sequence that is selected and related scan parameters.
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Scan Parameters 0 Sequence
The Sequence section of the ScanParameterList window (figure 6-1 0) contains
the fo llowing parameters:
Figure 6-10. The Sequence section of the ScanParameterList window.
Slice Plane - Provides the following options for the plane of the slices, as
shown in figure 6-11:
• AX- Axial
• SAG - Sagittal
• COR-Coronal
• SA-Sagittal and axial
• CA- Coronal and axial
• SC-Sagittal and coronal
• SCA- Sagittal, coronal, and axial
Figure 6-11 . Slice Plane options.
20 /30 - Provides the following options for the acquisition mode, as shown in
figure 6-12:
• I D - One-dimensional acqu isition. Used only in spectroscopy (lD is
automatically selected when Sequence is MRSSE).
• 2 0 - Two-dimensional acquisition. One slice is acquired per TR.
• 3D- Three-dimensional acquisition. ln 3D acquisitions, data encoded with
s lice pos ition information is collected, in addition to phase encoding and
frequency encoding. Multiple slices of image data are reconstructed us ing the
3D Fourier conversion. 30 acquisitions can produce images with varying s lice
thicknesses.
Figure 6-12. Acquisition mode options.
6. 11
0AS Is~ MRI System Reference Manual Th41hU ... tMqnet
Note: With 30 measurements, the SNR of images is lower at the top and bottom of each slab compared to the center area, making the images susceptible to artifact when using the BASG sequence. Therefore, position the region of interest so that it comes to the center of the slab and set the number of slice encode a little higher.
Note: If homogeneity of the magnetic field is poor, BASG is vulnerable to magnetic field distortion and degraded image quality due to the generation of artifacts. To minimize this effect, be sure to carry out volume shimming before performing the BASG scan.
Note: If the blood currents often run parallel to scanned slice or slab, if they wind drastically, or if their transit paths substantially differ between the right and left vessels, the MRA image should be carefully interpreted.
Note: Slice scan, slab scan, and pre-saturation pulses should be positioned to maximize the TOF effect when scanning with TOF MRA.
Note: Check original images concurrently while interpreting TOFMRA.
6. 12
Sequence- Provides the following options for pulse sequence, as shown in
figure 6- 13:
SE (Spin Echo)- Produces images with
proton density, Tl , and/or T2 weighting.
1§111§·+
• IR (Inversion Recovery) - Uses a 180° inverting radio
frequency (RF) pulse prior to the 90° excitation pulse to
acquire images with specific suppression .
• GE (Gradient Echo)- Uses a variable flip angle to
acquire images with T J or T2* contrast. The contrast
weighting is primarily determined by the flip angle.
FSE Scanogram SE IR GE SARGE RSSG TRSG BASG uTE FSE FJR pnmeFSE primeFJR isoFSE TOF PC SEEPI GEEPI OWEPI RSSG EPI Shim s.Map MRSSE T2RelaxMap
• SARGE (Steady State Acq uisition with Rewound
Gradient Echo)- Uses closely-spaced RF excitation pulses and shott TR (repetit ion ti me)
to create a steady-state signal. Th is sequence
produces images with Tl and T2 weighting.
• RSSG (RF Spoiled SARGE)- Uses c losely
Figure 6-13. Pulse Sequence options.
spaced RF excitation pulses with variable phase shifts. Th is sequence
produces images with Tl weighting.
• TRSG (Time Reversed SARGE)- Acquires the signal that was excited by the
prior RF pulse. This sequence produces images with heavy T2 weighting.
• BASG (Balanced SARGE) - Uses a short TR and acquires the signal under a
steady state, with slice-, phase-, and frequency-rewinder pulses. Th is sequence
produces images w itJ1 high signal-to-noise ratio (SN R), mixed Tim contrast,
and bright fluid.
• 11TE (micro Echo Time) - Used to detect tissue with an extremely short
transverse relaxation time (T2).
• FSE (Fast Spin Echo)- Uses multiple 180° RF pulses to more rapidly
produce images with proton density, Tl , and/or T2 weighting.
• FIR (Fast Inversion Recovery) - Uses a 180° inverting RF pulse prior to ilie
90° excitation pulse to acquire images with specific tissue suppressions.
• primeFSE-Similar to FSE, except that the user can enter T E and bandwidth
values, rather than values for the Inter E. Time (echo interval) and Echo Shift
parameters (these parameters are described later in this chapter).
• primeFI R- Simi Jar to Fl R, except that the user can enter T E and bandwidth
values, ratJ1er than Inter E. Time and Echo Shift parameter values.
• isoFSE (Isotropic Fast Spin Echo)-Optimized 30 FSE sequence that allows
an isotropic (or near isotropic) volume acquisition to be acquired, from which
sl ices can be reconstructed in any plane, thickness or interval desired.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: Image quality with EPI depends largely on the homogeneity of magnetic field. Volume shimming is required before running SE EPI to achieve good 1mage quality.
Note: In the S.Map sequence, scanning is carried out with the coil used for the main scan and the TR body coil.
The S-Map sequence is sensitive to patient movement. Keep the patient as still as possible while S-Map scanning to avoid artifact.
When scannmg the abdominal region, breath holds are required in an S·Map sequence when Mode is Normal.
When Wait mode is ON, the system pauses twice: after the prescan and in the middle of the S-Map sequence.
The wide area is to be scanned using the TR body coil. The scanogram should be used with the coil for the main scan. Therefore. make sure that the area which is not scanned through the scanogram does not cause artifact.
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Scan Parameters c;)
• TOF (Time of Flight)- Used to produce MRA using flow/inflow resu lts of
blood.
• PC (Phase Contrast)-Optional. Produces MR angiographs using phase
infonnation of blood flow.
• SE EPI (Spin Echo using Echo Planar Imaging) - Produces images with T l
or T2 weighting using very short acquisition t imes.
• G E EPI (Gradient Echo using EPI) - Produces images with T2* weighting
using ve1y short acquisition times.
• OW EPI (Diffusion Weighted EPI)- Produces diffusion-weighted images,
which depict the restriction of water molecule diffusion.
• RSSG EPI (RF Spoiled SARGE using EPI)- Optional. Produces images with
T I weighting using short acquisition times.
• Shim (Shimming)- Performs highly-precise corrections ofthe static
magnetic fie ld.
• S-Map (Sensitivity Map)- A sequence dedicated to 3D sensitivity map
acquisition. Acquires 30 sensitivity data to be used for shading correction
and RAPID measurement. Tn this sequence, images (acquired data) are not
displayed.
• MRSSE (MR Spectroscopy using Spin Echo)-Optional. Acquires molecular
dens ities of metaboliz ing substances in the human body.
• T2Relax.Map- Used to acquire multiple echo images at various T E times to
calculate the T2 relaxation times for every pixel in the image.
ADAGE
Multiple gradient echoes (typically three to six) are added together to form one
image for improved signal and contrast. With the ADAGE techn ique, multiple
echoes from a gradient echo (GE) sequence are combined to output an image
with improved SNR and/or CNR. Combine is automatically selected from Calc.
Image when Sequence is GE, SARGE, or RSSG and more than 3 echoes are
set to be acquired.
Target-Sets the type oftarget. Available only when Sequence is isoFSE.
• Tissue- A scan is performed with A ip angle of RF Refocus pulses modulated
for tissue.
• Fluid - A scan is performed with flip angle of RF Refocus pulses modulated
for fluid.
EchoTime Mode-Sets the range for the echo time (figure 6-14).
When Sequence is SE, choose one of the following:
• Nonnai - Use for normal scanning.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
Note: When scanning a patient with an orientation other than feet first supine, the output image has it's orientation rotated, but shimming is not affected.
Note: When scanning with the patient oriented feet first, the output images are in the reverse order of the slice order being set, but shimming is not affected.
6. 14
• Short TE-Use to acquire images with shorter TE than the Normal setting;
however, some parameters such as Dua l Slice and Multi Echo will be restricted.
When Sequence is FSE, FIR, p rimeFSE, or pr imeFIR, choose one of the
following:
• Shortl ET - Use to acquire images with short Inter E.Times, such as 12 and
below. In figure 6-14, ShortiET is selected.
• LongiET -Use to acquire this slice images with Inter E.Times of 12 and
above. This selection is used in FIR imaging.
• Optimized-Use to acquire the higher SNR and less aliasing image with same
Inter E.Time as ShortlET. O ptimized is available for 30 acquisition only.
Figure 6-14. The Echo Time Mode scan parameter.
Mode-Selects the sequence mode.
• Normal- Normal measurement is performed.
• YASC-ASL (optionai)-Creates an image oftluids, such as labeled blood
flow, using a spatial selection IR pulse. When VASC-ASL is selected, m Pulse is displayed and set to Selective.
• GEIR- Performs segment measurement using an IR pulse as a prepulse.
When GEIR is selected, IR P ulse is displayed and set to Segmented. As a
segment becomes larger, contrast may be slightly blurred. Water excitation is
available with GEIR.
• TIGRE- Performs a high-speed Tl contrast measurement in combination
with a fat suppression pulse for frequency selection. When TIGRE is
selected, Saturation is displayed and set to Segm ent FS.
• Nest-Collects signals using the receiver coil and Transmit/Receive Body
coil at nearly the same tin1e during the S-Map sequence. A sensitivity map
not easily affected by movement can be created for regions where movement,
such as breathing, is monitored.
• YASC-FSE-A Fast Spin Echo mode developed for non-contrast PYA
applications. VASC-FSE performs an acquisition in systole and another in
diastole. The difference between the two acquisitions is subtracted to obtain
blood vessel images of either arteries or veins.
Shim Mode- Provides options for the use of shimming results (figure 6-15).
• off-Does not use shimming results.
• Volume- Uses volume shimming resu lts. Shimming results are not used
when there are changes in a patient or coils.
• Auto Volume - When measurement conditions include shim measurements,
shimming is automatically performed during prescanning.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 • Regional - Performs regional shimming in a specific area designated by the
purple box on the positioning screen. Upon opening a scan task, the regional
shim box moves along with any movement of the slice group. However, once
the regional shim box is activated, the slice group and regional shim no longer
move together.
!It Caution
Volume
off Volume AWlVolume R onal
Figure 6-15. Shim Mode options.
If an error occurs during shimming, contact Hitachi service.
Additiona l Notes for the Mode pa ra meter :
The values that can be set may be limited by the selected Sequence and related
scan parameters.
Since GElR is 3D measurement, the SNR of images is lower at the top and
bottom of each slab compared to the center area . Therefore, position the region
of interest so that it comes to the center of the s lab and set the number of slice
encode a little higher.
Pre-saturation pulses may be used with the 3D GEIR sequence, however MTC
and FatSat pulses cannot be used.
Additiona l Notes for the Shim Mode parameter :
Estimated fie ld distributions are displayed after volume shimming. however they
are not displayed after regional shimming.
The vo lume of interest (VOl) must be within the region of volume shimming.
The results of shimming are canceled and become ineffective when the patient
name or receiver coi l is changed, when Shim Mode is off and any measurement
is carried out, or when Prescan is ON and any measurement is carried out.
When Shim Mode is set to anything other than Regional, the VOl is deleted.
The region of shimming, region of imaging, and the direction of phase encoding
should be identical.
The center of shimming shou ld be identical with the center of the magnetic field.
Additiona l Notes for the S-Map pa ra mete r:
The position and the scan parameters should be set in a way that prevents
aliasing artifact from occurring in the area selected for the main scan.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
Note: If performing a Black Blood scan with Multi Slice and Multi Acquisition= 1, adjacent slices are excited in 1 TR, so image quality can be degraded. Perform scans with the slice interval larger than the slice thickness of the Double IR Pulse and STIR Pulse or with Multi Acquisition ~ 2.
Note: The values that can be set may be limited by the selected Sequence and related scan parameters.
6. 16
Planes to be scanned wi ll vary depending on the anatomical region being
scanned. Therefore to avoid aliasing a1tifact, COR and SAG planes are
recommended because the direction of the body axis is the readout direction.
When setting FOY, it is recommended to set it 20 to 30 percent larger than the
one for the main scan.
Slab thickness shou ld be set accord ing to the size of the region to be scanned,
adjusting S. Encoding.
SNR can be too low when FOY is smal l. Therefore, it is necessary to ensure
adequate SNR by setting the appropriate NSA.
Oblique-Provides methods for determ ining whether or not scans can be
performed, based on the angulation of slices. Options are (figure 6-16):
• Full -Allows fu ll angulation of slices, but will require protocol changes if a
steep angle is used.
• Limited-Allows a limited degree of angulation, so that the protocol
parameters selected for the acquisition can be used.
Seq. Parameter
r+ii ~~L=--im-=itec:...d --~ Full Limited
Figure 6-16. Oblique methods.
Figure 6-17 shows the Seq. Parameter section of the ScanParameterList window:
Figure 6-17. The Seq. Parameter section of the ScanParameterList window.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: TE2. TE3. and TE4 are used only for multiple echoes.
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Scan Parameters 0 FOV-Indicates the s ize in millimeters ofthe visual field to be reconstructed
fo llowing the scan.
FOV2-Sets the size ( in millimeters) of the longitudinal visual ·field
reconstructed fol lowing the scan. The c rosswise visual field is set by the FOV
parameter. Used on ly in spectroscopy (FOV2 is displayed when Sequence is
MRSSE).
TR- lndicates the repetition time in milliseconds of the pulse sequence. During
gated scans, TR values are automatically set when Trigger is selected for the
Gate or Resp mode.
TE- Indicates the echo period in milliseconds for the first echo. This value is
automatically set when the following are selected from the Sequence list:
• BASG • FSE
• FIR • Shim
TE2- Ind icates the echo period for the second echo. This setting is displayed
when the selected Sequence is SE, GE, SARGE, RSSG, or FSE, and the
Multi Echo parameter is set to 2 or more. (When FSE is selected, TE2 is
automatically set based on other parameters, such as E.Factor .)
TE3- Indicates the echo time for the third echo. This setting is displayed when
the selected Sequence is SE and the M ulti Echo parameter is set to 3 or more.
TE4- Indicates the echo time for the fourth echo. This setting is displayed
when the selected Sequence is SE and the M ulti Echo parameter is set to 4 or
more.
Figure 6-18 shows settings fo r the TE through TE4 parameters.
Figure 6-18. Example settings for TE, TE2, TE3, and TE4 boxes.
Delta TE - Indicates the time between echoes. This parameter is available
when Sequence is SARGE (20 ), GE, or RSSG and the Multi Echo parameter
is greater than 2.
Last TE - Indicates the echo time for the last echo. This parameter is available
when Sequence is SARGE (20), GE, or RSSG and the Multi Echo parameter
is greater than 2.
6. 17
0AS Is~ MRI System Reference Manual nt.htletllqnet
Note: TEequiv is the echo time needed in an isoFSE scan to obtain the same contrast as TE in a conventional FSE scan. However the exact same contrast cannot be obtained due to T1 decay contamination.
Note: When Excitation Pulse is Non· selective, aliasing artifact may appear in the slice direction. Make sure the imaging area covers the entire imaging object in the slice direction, or apply presaturation pulses to both edges of a slab to suppress aliasing artifacts.
Note: AdditionaiiR pulse options (Double, Triple) are associated with the CardioSuite, which is a purchasable option.
Note: Tl and FatSat cannot be combined simultaneously in the STIR type fat suppression.
Note: Optimum Tl of the Black Blood scan varies depending on orientation of the slice plane. When reduction of blood signal is small, modify Tl and retry the scan.
6. 18
TEequiv- Represents the echo time needed in an isoFSE scan to obtain the
same T2 contrast as a conventional FSE scan. This parameter is ava ilable when
Sequence is isoFSE. Set TEequiv equal to the TE setting in a conventional
FSE scan to obtain t he same contrast.
Excita tion Pulse- This parameter is displayed when Sequence is isoFSE and
is fixed to Non-selective.
FA (Flip Angle) - The angle of excitation to which the net magnetization is
tipped relative to the main magnetic field.
IR Pulse (Inversion Recovery Pulse) - Indicates if an IR pulse w ill be used for
tissue saturation. This is primarily used with Cardiac scanning.
This parameter can be selected when Sequence is SE, BASG, FSE, DW EPI,
SE EPI, or GE EPI.
The following options are available, as shown in figure 6-19:
• Off- Does not perform tissue saturation; this is the recommended setting.
• Single- Performs tissue saturation with designated Tl.
• Double- Executes blood saturation via Double-1 R. When Double is selected,
TI becomes available.
• Triple (optional)-Executes fat saturation via STlR pulse and blood saturation
via Double-IR. When Triple is selected, TI and Tl2 become available.
• Segmented- Performs segment measurement using the STIR pulse as a
fat suppression prepulse. Segmented is selectable with 3D RSSG (GEIR
imaging). When Segmented is selected, TI and Segment become available.
• Se lective-Applies a spatial selection IR pu lse. Selective is selectable with
VASC-ASL imaging. When Selective is selected, TI and Segment become
available.
off
off L s ingle
Figure 6-19. Example IR Pulse options.
TI-Sets the Inversion Time, wh ich is the time period between the initial 180°
inversion pulse and the 90° excitation pulse in an IR pulse sequence. This box
is available when the selected Sequence is IR or FIR, the ECG Gate Mode is
Delayed or MyoPer, or when IR Pulse is Single. The measurement of the Tl
wil l be calcu lated as follows:
• When Sequence is IR or FIR, or IR P ulse is Single, TI is the interval
between the STIR pulse and the excitation pulse.
• When Gate Mode is Delayed or MyoPer , Tl is the interval between the STIR
pu lse and the zero encode excitation pulse.
Copyright@2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: For a FLAIR sequence of the brain, the IR Thk.Ratio should be set to 4.0.
Note: The gap between slices can be calculated as: Interval- Thickness = Gap
QS4-86717v3
Scan Parameters 0 • When IR Pulse is Double or Triple, T l is the interval between the Double-lR
pulse and the excitation pulse.
• When IR Pulse is Segmented or Selective, TI is the e lapsed time from the
STTR pulse to the zero encoded excitation pulse.
TU- Sets the interval (in milliseconds) from the STIR pulse to the excitation
pulse. Specify a TU setting when IR P ulse is Tr·iple.
Segment- Sets the number of echoes to be acquired after application of one
STIR pulse. Specify a Segment setting when IR P ulse is Triple.
lRFA- Sets the excitation angle (in degrees) of the IR Pulse spin. Specify an
IRFA setting when Gate Mode is MyoPer .
TR Thk.Ra tio- lndicates the s lice thickness selection of the initial 180° pulse
relative to the slice d1ickness of ilie main scan. The normal setting for this
parameter is 1.3. You can use this parameter when Sequence is FIR or Prime
FIR, or when Sequence is FSE or P rime FSE; and IR P ulse is Single. In figure
6-20, the Sequence is FIR and theIR Tbk.Ratio is set to a value of 1.3.
Figure 6-20. IR Thk. Ratio example.
BBJR Thk.Ratio - Sets the s lice thickness ratio of the Double-lR Pulse for the
main scan sl ice thickness. Specify a BBIR T hk.Ratio when Sequence is FSE
or primeFSE and TR P ulse is Double or Triple.
Thickness - Indicates the s lice thickness (in mill imeters). When Thickness is
changed, Interval automatically updates to maintain the gap between slices.
Interval- Indicates d1e spacing (in millimeters) between slices, measured
from the center of one s lice to the center of the next slice. The interval in 20 multi-slice acquisitions is between parallel slices; the interval in 30 multi-slab
acquisitions is between parallel slabs. Interval automatically updates when
Thickness is changed, thus maintaining the gap between slices.
Multi slice- Indicates the number of slices to be acquired during one scan.
This setting is displayed for 20 acquis itions only.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
6 • .20
Multi Echo- Indicates the number of echoes to be collected in one scan. As
the Multi Echo value is increased, add itional numbered TE boxes (TE2, TE3,
and so on) become available on the ScanPar·ameterList window. Multi Echo is
available when Sequence is SE, FSE, GE, SARGE, or RSSG. In figure 6-21,
Sequence is GE and Multi Echo is set to a value of2.
Figure 6-21. Multi Echo example.
Multi slab- Available for 3D acquisitions only. Indicates the number of slice
slabs to be acquired in one scan. In figure 6-22, Sequence is TOF and Multi
slab is set to a value of 4.
Q\1!@119 TOF @id4@ r~-o-lum-e-~~.~1
&pi- Umited Seq. Parameter
'" 1220 1· 1·] i· 22.0 1· 1· i 8.7 1-· .. II 25 I . .. I !!Aid 1.0 I·· .. ,.
~ =t:t1 !il.!.ii!&i '*·'·9"' 1~0 1· ..
. . .
Ufi•M· Figure 6-22. Multi slab example.
Recon P itch - Allows the desired thickness of the reconstructed slices to be
input. Recon P itch can be a value no less than one-half of the acquired slice
thickness (the Thickness parameter).
Recon P itch will automatically adjust to maintain the ratio between Thickness
and Recon Pitch values. Additionally, Recon Pitch automatically reverts to
upper and lower limits when an entered value exceeds either limit (the upper
limit is T hickness, and the lower limit is one-halfofThickness).
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 Recon Slice- The number of slices to be reconstructed for the acquis ition.
Slice Rejectl % 1- lndicates a percentage of slices at the slab ends that wi ll not
be reconstructed. This is useful for 3D acquisitions that may have decreased
SNR at the s lab ends. One half of the value that is se lected is rejected trom each
end of the s lab (for example, if20 percent is se lected, I 0 percent of the tota l slab
will be rejected from each end).
Overlapi% ]- Jndicates a percentage amount of slab overlap, wh ich is used
to improve the s ignal continuity between slab intervals in 3D TOF multi-slab
acquis itions. The Multi slab parameter must have a value greater than I.
Figure 6-23 shows the Slice#, Slice Rej ectl% 1, and Overlap[% ] parameters set
for a 3D TOF series.
Figure 6-23. Slice#, Slice Reject[%], and Overlap[%] example.
Multi Acquisition - Indicates the number of acquis itions. This setting is
available when the Mode parameter is Interleaved or Sequentia l.
When Mode is Stack, the value in M ulti Acquisition is unavailable, but will be
the same as the value set in the Stacks box, as shown in figure 6-24.
~!''!'!"!'!'!! 2 4&G ~~==ck===r~ • [ 1· !· .
Figure 6-24. Multi Acquisition example.
When the Mode parameter is SingleSlicc, M ulti Acquisition is unavailable.
However, the d isplayed number of acqu isitions will be the same as the number
set in Multi slice for 20 acquisitions, or the number set in Multi slab for 3D
acqu isitions, as shown in figure 6-25.
Multi slab Multi slice
Figure 6-25. SingleS/ice Mode examples for 20 and 30 acquisitions.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
6 . .2.2
The following examples explain how the M ulti Acquisition, Mode, and
M ulti slice parameters can be set in various combinations to acquire images
differently.
Example 1: M ulti slice is 6, Mode is Interleaved, and M ulti Acquisition is 2.
The value of2 in the M ulti Acquisition box divides the sl ices into two groups
of three slices each. The I nterleaved mode acquires the top and bottom slices,
then the middle slice in each group, all with the same TR. For these parameter
settings, the first acquisition would be slices I and 3, and then slice 2; the second
acquisition would be slices 4 and 6, and then slice 5.
Example 2: M ulti Slice is 6, Mode is Sequentia l, and M ulti Acquis ition is 2.
The value of2 in the M ulti Acquisition box divides the sl ices into two groups
ofthree slices each. The Sequential mode acquires the slices in numerical order,
one group at a time, all with the same TR. For these settings, the first acquisition
would be slices 1, 2, and 3; the second acquisition would be slices 4, 5, and 6.
Example 3: M ulti Slice is 6, Stacks is 2, and Mode is Stack.
Stack mode can be used when slices are set at different angles, such as in axial
lumbar imaging. Stack mode acquires the slices in the first stack, then the slices
in the second stack, all with the same TR. For these parameter settings, the
setting of the Stacks value at 2 with Mode set to Stack causes the M ulti Slice
box to be updated and display a total of 12 slices (6 slices x 2 stacks= 12 total
slices).
Example 4: M ulti Slice is 6 and Mode is SingleSlice.
SingleSlice mode is used to acquire one slice perTR, as in 20 TOF sequences.
For these parameter settings, each slice (of the 6 total slices) will be acquired
individually.
Mode-Specifies the acquisition mode. The options, as shown in figure 6-26,
are:
• Interleaved -Slices are acquired in an odd- and even-numbered fashion (such
as slice numbers I , 3, 5, 7, then slice numbers 2, 4, 6, 8).
• Sequential -Slices are acqu ired in order of slice number (such as 1, 2, 3, 4).
• Stack-Slices are acquired for each angle.
• SingleSiice- Each slice is acquired as a separate acquisition, with the
selected parameters (one slice per TR).
- Interleaved Interleaved Sequenbal Stack SingleSiice
Figure 6-26. Mode options.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 Slice#- Indicates the number of slices to be reconstructed for 3D acquisitions
(figure 6-27).
Figure 6-27. Slice# example.
Stacks- Indicates the number of groups when acqu iring multiple groups with
different angles.
Freq#- lndicates rhe number of sampl ing steps in the frequency axis, as shown
in figure 6-28. Hold the mouse pointer over the Freq# box to view the range that
is available.
IM §s6 ::J .. ' ..
Figure 6-28. The Freq# parameter.
Phase# - Indicates the number of sampling steps in the phase axis, as shown in
figure 6-29. Hold the mouse pointer over the P hase# box to view the range that
is available.
Figure 6-29. The Phase# parameter.
Freq Point- Sets the frequency resolution. Used only in spectroscopy (Freq
Point is displayed when Sequence is MRSSE).
ReconMatrix - Indicates the reconstruction matrix for the image. A value
larger than the frequency encoding value (from the Freq# box) and/or the phase
encoding value (from the P hase# box) can be set, in increments of32 (from 128
to 512).
6· 23
0AS Is~ MRI System Reference Manual T'MhtJent MqHt
Note: A value must be entered in the APR[%} box to make Half Scan available.
NSA (Number of Signals Averaged)- Indicates the number of s ignal
acquisitions to be averaged. Increasing NSA will improve the SNR ofthe image,
but also increases scan time. Doubling NSA doubles the scan time, but only
increases the SNR by approximate ly 40% because increased noise accompanies
the increased number of signals.
APR[%] (Asymmetric Projection Rate)- lndicates a percentage ofK-space
that w ill not be acquired in the phase encoding d irection. K-space as a whole is
I 00%; the APR[%J parameter can be set to values between 0% and 45% and
can be changed by 5% intervals. This parameter is used in conjunction w ith
Half Scan.
The position of the non acquired K-space region changes for each of the echo
layouts, as shown in figure 6-30. In addition, processing of the non acquired
region c hanges according to the setting of the Half Scan parameter (described
next in this section).
Frequency Frequency Frequency Frequency
PhaseW 4 PhaseW 1 PhaseF 1 Phase~ 5
6-24
3 2 2 4 2 3 3 3 1 4 2 1 4 1
APR APR APR APR
Centnc Ant1 Centnc Sequential ADA
Slice
Phaser, APR
Slice
Phaser, 1 3 2
1 3 2 4 6 5
4 6 5 7 9 8
8 7 9 11 10 12
11 10 12 APR
PEAKS RPEAKS
Figure 6·30. K-space filling for various echo layouts.
Half Scan -Enables image acquisition in a sha tter time by limiting the
sampling of the phase axis inK-space. Spatial resolution is maintained, but
SNR is reduced. Images are created using the acquired data, combined with the
interpo lated data used to fi II the non acquired region of K-space. Acquisitions
are performed in accordance with the val ues set for the phase direction in the
APR[%] parameter. The options, as shown in figure 6-3 l , are:
Copyright@ 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: OW/ is sensitive to movement smce the MPG pulse is applied. In multi-shot measurements, use gated scanning with the scan region immobilized to reduce motion artifacts.
QS4-86717v3
Scan Parameters 0 • off-Does not use Half Scan.
• ON-Uses Half Scan.
"'""' off ·~ off ON
Figure 6-31. K-space filling for various echo layouts.
The following examples explain how the APR(%} and Half Scan parameters
function together:
Example 1: APR(%] set at 25 percent and Half Scan is ON (figure 6-32)
This is the equivalent of~ Scan. Data is acquired from three-foUJths (~)or 75% of K-space; one-foUJth ( '.!.!)or 25% of K-space is interpolated.
:1*'1'111[5 :J .. €MIA*'' ( ON ·I
Figure 6-32. The equivalent of three-quarter scan.
Example 2: APR(%] set at 45 percent and Half Scan is ON (figure 6-33)
This is the equivalent of 1/ 2 Scan. Data is acquired from 55% of K-space; 45% of
K-space is interpolated.
1'1''1'1111~~45=-~~---IMIP*ii I ON ·I
Figure 6-33. The equivalent of one-half scan.
Shot Num.- Indicates the number of RF excitations, or TR periods, needed to
acquire data, as shown in figure 6-34. A lower shot number results in a faster
scan time. The shot number can be calculated using the fo llowing equation:
Phase# "'" E. Factor = Shot Num.
Figure 6-34. Shot Num. example.
Shot Num. is available when Sequence is SE EPl, DW EPL or GE EPI. Hold
the mouse pointer over the Shot Num. list to display the range of settings.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
Note: When Echo A/foe. is Centric and if# RF Prep is extremely small, good images cannot be obtained since data acquisition starts while steady state has not yet been reached.
6 • .26
Shot Num. is displayed, but unavai lable, in the following cases:
• Sequence is FSE, FIR, RSSG or EPI.
• Sequence is Prime FSE or Prime FIR, and Echo Alloc. is Centric.
E.Factor - The number of echoes to be used to create a s ingle image. An
acceleration rate is obtained based on the number of echoes used. However, the
more the echo is delayed, the weaker the signa l strength becomes due to the
decay of signal amplitude (T2 or T2*). As the E.Factor increases, the SNR and
resolution decrease.
E.Factor is avai lable when Sequence is FSE, FIR, or RSSG EPJ.
E.Factor is displayed but unavailable in the following cases:
• Sequence is SE EPI, DW EPI, or GE EPI.
OR
• Sequence is P rime FSE or Prime FIR, and Echo Alloc. is ADA.
Inter E. Time- The time between echoes. Inter E.Time is displayed when
Sequence is any of the following: FSE, FIR, SE EPI, DW EPI, GE EPI, or
RSSG EPI. When Sequence is FSE or FIR, an effective TE is calcu lated by
the system. This TE calculation inc ludes the E.Factor, Echo Alloc., Echo Shift,
and Inter E. Time parameters to determine image weighting.
Echo Shift-Adjusts image contrast by changing the location of the effective
TE in K-space, without changing the number of echoes. An Echo Shift of 1
changes the effective TE by an increment equa l to the value displayed in Inter
E. Time. Echo Shift is available when Sequence is FSE, FIR, SE EPI, GE
EPI, RSSG EPI, or DW EPI. Echo Shift is displayed but unavailable when
Sequence is Prime FSE or Prime FIR.
Echo Shift2 - AIIows Echo Shift to be selected for the second echo. Echo
Shift2 is available when Sequence is Prime FSE or Prime FIR.
Echo Alloc. - AIIows the echo layout method to be selected. A pa11ial listing of
options is shown in figure 6-35.
The options are:
• Sequential
• Centric
• AntiCentric
Centric Ant1Centnc
Figure 6-35. Echo A/foe. options.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 • ADA (Asymmetric Data Allocation)
• PEAKS (optional)
• RPEAKS (optional)
• TPEA KS (optional)
• Seq-Seq (optional)
• Cent-Cent (optional)
• Cent-Seq (optional)
• Cir-Raster (optional)
• C ir-Centric (optional)
• Cir-Anti Centric (optional)
All of these Echo Alloc. commands are available when Sequence is isoFSE.
Sequential, Centric, AntiCentric, and ADA are frequency/ phase 2D echo
layouts (figure 6-36).
The non acquired region will be determined in combination with the value set in
the APR[% J parameter. Processing of the non acquired region will change
according to the Half Scan parameter value. For example, Half Scan is
automatically set when ADA is selected.
Frequency
PhasefC 4
Frequency
Phaseff 1
Frequency
Phase.fe 1
Frequency
PhaseW 8 3 2 2 7 2 3 3 6 1 4 4 5 1 4 5 4 2 3 6 3 3 2 7 2 4 1 8 1
Centnc Ant1 Centnc Sequential ADA
Figure 6-36. Frequency/phase 20 echo layouts.
PEAKS and RPEAKS are optional phase/slice 2D echo layouts (figure 6-37),
wh ich are used during 3D contrast-enhanced MRA. Acquisition is started
in the direction of the epicenter of K-space. When the epicenter is acquired,
acqu isition is performed receding from the epicenter. When the APR[%]
parameter is 0, there is no difference between PEAKS a nd RPEAKS. However,
when the APR[% ] parameter is set to anything above 0, the non acquisition
region differs. Processing of the non acquired region changes according to the
Half Scan parameter value.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
6 . .28
Slice
Phaser,
1
4
8
11
APR 3 2
6 5
7 9
10 12
PEAKS
Slice
Phaser, 1
4
7
11
3 2
6 5
9 8
10 12
APR
RPEAKS
Figure 6-37. PEAKS and RPEAKS optional phase/slice 20 echo layouts.
TPEAKS is an optional phase/slice 2D echo layout, which is used during 3D contrast-enhanced MRA in the same way as PEAKS and RPEAKS. The
distance between the center of the phase/slice plane and each acquisition point is
used as the standard to set the acquisition order. As shown in figure 6-38,
acquisition is performed from the center of the phase/slice plane, with the time
that K-space data collection begins as the peak of the contrast agent density.
Acquisition is then performed on the side closest to the center.
Slice
Phaser,--------------~
4
Figure 6-38. TPEAKS optional phase/slice 20 echo layout.
Seq-Seq is selectable on ly with 3D RSSG (GEJR imaging). The measurement
order of both phase encode and slice encode is Sequential. With Seq-Seq, temporal efficiency is better than Cent-Seq and Cent-Cent since data is
acquired before the Tl time.
Cent-Cent is used with 30 RSSG (GEIR) or TIGRE imaging. Echo allocation
for both the phase and slice encode directions is Centric. When using this echo
allocation, #RF Prep must be increased. However, increasing #RF Prep results
in the reduction of fat suppression by the FatSat pulse.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 Cent-Seq is an echo allocation option for TIGRE imaging. Echo allocation for
the phase encode direction is Centric, while the echo al location for the sl ice
encode direction is Sequentia l. Centric scans from the center of K-space toward
the peripheral region, while Sequential scans from the peripheral region toward
the center, sequentially.
Figure 6-39 illustrates the Seq-Seq, Cent-Cent, and Cent-Seq echo allocation
options.
I
I
1
2
3
4
5
Seq-Seq
Q) '0
8 c: w
~ t Q.
4 3
r---1 2
Slice Encode
I I
3 2
1
1 2
3
Cent-Seq
Q)
8 c: w
~ t Q.
l
-3 2
1
I
3 2
1
1
2
3
Cent-Cent
4
Slice Encode
---'1 1
2 3
Slice Encode
Figure 6-39. Seq-Seq, Cent-Cent, and Cent-Seq echo allocation options.
Cir-Raster is available only when Sequence is isoFSE. With Cir-Raste r,
the echo train is a llocated along the phase encode axis (ky). Data is acqu ired
sequentially from the edge ofk-space. This echo allocation is su itable for T2W
imaging.
Cir-Centric is available only when Sequence is isoFSE. With Cir-Centric, the
echo train is allocated a long the radial axis (kr). Data is acquired from the center
to the edge ofk-space. This echo allocation is suitable for PDW (proton dens ity
weighting) imaging.
Cir-AntiCentric is available only when Sequence is isoFSE. With Cir
AntiCentric, the echo train is a llocated along the radial axis (kr). Data is
acquired from the edge to the center ofk-space. This echo allocation is suitable
for heavy T2W imaging.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
6-30
Figure 6-40 illustrates the Cir-Raster, Cir-Centric, and Cir-AntiCentric echo
allocation options.
2 3 4
Cir-Raster
Cir-Centric Cir -AntiCentric
Figure 6-40. Cir·Raster, Cir-Centric, and Cir·AntiCentric echo allocation ophons.
Echo Skip - Allows echoes with different polarity to be skipped. Skipping
echoes does not affect the number of echoes to be obtained . Echo Skip is
available for display only and is fixed at ON.
3D Acq. Mode-Selects the measurement fie ld of the ky-kz plane (K-space), as
shown in figure 6-41.
II Circular ~
Normal 1 Circular
Figure 6-41. 3D Acq. Mode options.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 • Normal - Measures the rectangular field in the ky-kz plane (figure 6-42), when
Cent-Cent or Cent-Seq echo allocations are used with TIGRE.
kz -t--1!-1~----..-...----.
r~~
----. ky Normal
Figure 6-42. Normal 3D Acq. Mode K-space measurement field concept.
• Circular - Measures the inscribed circle in the rectangular field of the ky-kz
plane (figure 6-43). Circular is used to decrease scan time or increase
resolution while maintaining scan time. C ircula r is available when Sequence
is GE, SG, R SSG, or VASC-ASL.
kz
i ....... J...- r- t--...
/ '\.
" / r- vv
... ky Circular
Figure 6-43. Circular 3D Acq. Mode K-space measurement field concept.
C hemical Shift- Indicates the optimum polarity of the phase-encoding
grad ient magnetic fie ld. The polarity can be changed to minimize the effects
of image dist01tion. Chemical Shift is available when Sequence is SE EPI,
GE E Pl , DW EPI, or RSSG EPI, and Echo Alloc. is Sequentia l or ADA. As
shown in figure 6-44, the options are:
• Normal- Normal polarity of the phase encoding grad ient magnetic field.
• Reverse- Reverse po larity of the phase encoding gradient magnetic field.
6 ;;we ~Normal Normal Reverse
Figure 6-44. Chemical Shift options.
6. 31
0AS Is~ MRI System Reference Manual T'MhtJent MqHt
Note: The values that can be set may be limited by the selected Sequence and related scan parameters.
6-32
DE P ulse (Driven Equil ibrium Pulse)-An additional pulse that can be used
following signal coElection to possibly decrease TR and consequently decrease
scan time, while maintaining T2 contrast. A DE pu~se converges. the transverse
relaxation of the magnetization and forces it to longitudinal relaxation. DE
P ulse is available when Sequence is FSE, FIR, Prime FSE, or Prime FIR. The
following options are available, as shown in figure 6-45:
• off- Does not add the DE pulse.
• ON -Adds the DE pulse.
Figure 6-45. DE Pulse options.
M ult i Voxel-lndicates the number ofvoxels acquired in one scan. Used only
in spectroscopy (Multi Voxel is d isplayed only when Sequence is MRSSE).
Advanced
The Advanced section of the ScanParameterList window (figure 6-46)
contains many additional parameters that can be used during image acquisitions.
Figure 6-46. The Advanced section of the ScanParameterList window.
P resat (Presaturation)-AIIows presaturation pulses to be applied that can
reduce artifacts by controlling the signals from movable areas (such as blood
flow signal or the abdominal wall).
Pres.aturation is a technique that uses repeated RF excitation of structures
adjacent to the anatomy of interest to reduce or eliminate the phase effect
artifacts that can be caused by flowing nucle i in these adjacent structures. The
signal from the flowing nuclei is saturated, and therefore nullified, upon entering
the FOV.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: Refer to chapter 3-2 of the Oasis How-to Manual for complete presaturation pulse details.
QS4-86717v3
Scan Parameters 0 You can set a maximum of eight presats, with the Presat box displaying the total
number. The first two presats are automatically set as parallel regions adjacent to
the slice surface. These two regions prevent the blood flow s ignal from flowing
into the sl ice plane to be scanned. Presats are displayed in blue. The mouse can
be used to rotate, move, or magnify the pre sat regions.
Normal-Applies presats for each slice acquisition. Figure 6-46a shows a
normal presat.
Figure 6-46a. A Normal presat.
6· 33
0AS Is~ MRI System Reference Manual nt.hU•tMqJMt
6-34
Walking-Allows the position of the presat region to move, or "walk," for
each slice acquired (or each slab in 3D). In this manner, the presat always
remains adjacent to the slice. This is used when acquiring blood vessel images
in angiography.
Walking is avai lable when Sequence is TOF or BASG. If a walki ng presat is
selected, it is the first presat displayed in the viewp01t, and it is displayed in
green. Only one walking presat is available. The mouse can be used to rotate,
move, or magnify the wa lking presat region. The number displayed in the
Presat box is the total number of presats, including the walking presat. Figure
6-47 shows a walking presat.
Figure 6-47. A Walking presat.
Intermittent- Applies presats for each repetition time (which is the value set
in the TR parameter); normally, the presat is applied for each slice acquisition.
Intermittent presats will a llow you to increase the number of slices; however as
the TR increases, the effectiveness of the presat decreases.
The maximum number of intermittent presats available is 2. The intermittent
presats will be displayed in light blue. The mouse can be used to rotate, move,
or magnify the intermittent presats. The number displayed in the Presat box is
the total number ofpresats, inc luding the interm ittent presats.
Figures 6-48 and 6-49 show the Intermittent parameter with values of I and 2
respectively.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
----------------------------------------6 Scan Parameters 0
QS4-86717v3
Figure 6-48. lntennlttent set to 1.
Figure 6-49. lntennittent set to 2.
Segment- May improve presat results. Available when Sequence is BASG, and
one or more presats have been selected. Figure 6-50 shows Segment set to I.
Figure 6-50. The Segment parameter.
6·35
0AS Is~ MRI System Reference Manual 1'1MI hUnt llqnet
6-36
Dual Slice-Acquires twice as many images w ith the same scan parameters
by acquiring two parallel slices at a time. The number that can be entered in the
Multi slice box is doubled. An even number is required in the NSA parameter
box. Dual Slice is available when Sequence is SE, IR, or GE. The options for
Dual Slice, as shown in figure 6-51 , are:
• off- Does not use dual slice.
• ON-Uses dual slice.
Figure 6-51. Dual Slice options.
Rephase (Flow Compensation) - Used to suppress flow artifacts, such as blood
and CSF. The options, as shown in figure 6-52, include:
• off- No rephase.
• Sl ice- Rephase is applied along the slice direction only.
• Freq-Rephase is applied along the frequency direction only.
• Slice_Freq -Rephase is applied along the s lice and frequency directions.
lUFF off
off Slice Freq Slice Freq
Figure 6-52. Rephase options.
The available Rephase options depend on the selected Sequence. For multi
echo acquisit ions, the presence or absence ofRephase for each echo is as
follows:
Sequence l Echo 2 Echoes
SE No rephase Rephase
GE Rephase Rephase
SARGE Rephase Rephase
RSSG Rephase Rephase
FSE Rephase Rephase
primeFSE Rephase Rephase
F low R eduction-Available when Sequence is SE, the RADAR parameter
is ON, and the Rephase parameter is off. Flow Reduction allows the use of a
dephase pulse to dephase the blood flowing through a sl ice, useful when black
blood imaging the carotid arteries. The options include:
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: As the frequency bandwidth of the reception signal is reduced, the SNR of the image increases. However. chemical shift artifacts (a phenomena where the difference in the resonance frequencies between water and fat diverge on the image) will become noticeable.
QS4-86717v3
Scan Parameters 0 • off-No dephase.
• Slice - Oephase is applied a long the sl ice direction on ly.
Level-Sets the strength of the flow dephasing gradient magnetic field pulse. If
Level is changed, the suppression effects of artifacts due to blood flow change.
Level options include:
• Light- T he flow dephasing gradient magnetic fie ld pulse strength is light.
• Medium- The flow dephasing gradient magnetic field pulse strength is
medium.
• Heavy- The flow dephasing gradient magnetic field pulse strength is heavy.
Bandwid th[k llz] - lndicates the frequency bandwidth (kHz) of the reception
signal, as shown in figure 6-53. Since noise is distributed evenly across all
frequency bandwidths, reducing the frequency bandwidth value reduces noise
and improves the SNR; however, chemical shift artifacts may become more
noticeable.
Figure 6-53. The Bandwidth[kHz] parameter.
Bandwid th2[kHz] - lndicates the frequency bandwidth (kHz) of the reception
signal for the second and subsequent echoes during a multi-echo acquisition.
This parameter is available when Sequence is SE, GE, SARGE, or RSSG, and
M ulti Echo (under Seq. Parameter) is 2 or more.
In figure 6-54, M ulti Echo is set to 2, and Bandwidth2[kHz] is set to I 0.
04171 El:ll Ell
Figure 6-54. A Bandwidth2[kHz] parameter example.
6-37
0AS Is~ MRI System Reference Manual nt.htletllqnet
Note: The larger the AMI[%] value, the shorter the TE. However, if Half Echo is off, there may be a degradation of spatial resolution.
Note: Half Echo uses frequency direction data in the same manner that Half Scan uses phase direction data.
6-38
AMI[%] (Asymmetric Measurement Imaging)- Indicates the percentage
(usually 20% to 30%) of the early portion of the echo signal that will not be
measured, as there is more noise in the beginning of the echo signal (as shown
in figure 6-55). Asymmetric measurement imaging a llows the user to shorten the
TE and increase the number of slices, and may result in improved contrast on
Tl -weighted images. However, if AMI[% ] is set to 30% or higher without
setting Half Echo to ON, spatia l resolution may be degraded (Half Echo is
described next in th is section).
Frequency direction GC
_j: 100% .., , ~ ...
Asymmetric measurem imaging(%)
Echo signal---___{
Figure 6-55. AMI[%] illustration.
L
Half Echo-Prevents degradation of spatial resolution during AMI[%]. Half Echo creates an image by estimating the uncollected data (based on the
col lected data) in the frequency direction. It a llows for the use of a shorter TE,
or lower bandwidth. The options are:
• off- Does not use half echo.
• ON-Uses half echo.
Echo Type- Indicates the echo allocation method, and is fixed as Half.
Used only in spectroscopy (Half is automatically selected when Sequence is
MRSSE).
Rect .FOV (Rectangular Field of View)- Reduces the number of acquisit ion
points in the phase direction (set in the Phase# parameter). Rect.FOV is used to
match the size of the phase encoding direction for the scan target, as well as for
the FOY that has been set.
The scan time will be reduced by the amount that the value of Phase# is
reduced. Although the spatial resolution is the same as for a normal scan, the
SNR will be reduced in accordance with the number of reductions in the phase
encoding direction.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 As shown in figure 6-56, the options include:
• off- Does not use Rect.FOY.
• Auto-Acquires the size of the patient in the phase encoding direction, and
then automatically determines the FOY actua lly acquired and the number of
acquisition points in the phase direction.
• Manual - Allows the user to select the size of the rectangular FOY.
off
off Auto Manual
Figure 6-56. Rect.FOV options.
Size[% J- Available when Rect.FOV is Manual. Allows you to enter the size
of the rectangular FOV to be acquired; this value is displayed as a percentage of
the current FOV parameter (under Seq. Parameter). Figure 6-57 shows
Size[% ] set to 80, meaning the FOV will be reduced by 20% in the phase
encoding direction.
Figure 6-57. Size[%] example.
Anti.aliasing- Removes aliasing artifacts that are produced when the patient
is larger than the FOY in the phase encoding direction. Anti-a liasing is also
effective in reducing motion artifacts in certain anatomic regions (such as the
chest or abdomen).
As shown in figure 6-58, the options include:
• off- Does not use anti-aliasing.
• Auto - Acquires the size of the patient in the phase encoding direction. The
FOV that is actually acquired and the number of acquisition points in the
phase direction are automatically determined based on the value of the Mode
parameter, which is described next in this section. The available Mode options
are Res and Time.
• Manual -Allows the FOV size to be entered in the Size[% ] box. The
available Mode options are Res, T ime, and TimeRes.
lhPMIFiiii! off off Auto Manual
Figure 6-58. Anti.aliasing options.
6· 39
0AS Is~ MRI System Reference Manual T'MhtJent MqHt
Note:
If# RF Prep is set to an extremely low value, data with large signal variations will be acquired, causing artifact.
6-40
Mod e-Specifies the manner in which anti-aliasing is performed: maintaining
spatial resolution, maintaining scan time, or both. The following options are
always available:
• Res-Spatial Resolution Mode. Increases the number of acquisition points
in the phase direct ion according to the value ofthe Size[% ] parameter. The
spatial resolution is maintained, but the scan time increases based on the value
of the Size[% ] parameter.
• Time-Scan Time Mode. Increases the acquisition FOY according to the
value of the Size('% ] parameter, but does not change the number of acquisition
po ints in the phase direction . The scan time is maintained, but the spatial
resolution decreases based on the value of the Size[% ] parameter.
The following additional option is available when Anti.a liasing is Manual:
• TimeRes- Scan Time/Spatial Resolution Mode. Doubles the number of
acquisition points in the phase direction and automatically reduces the
effective NSA by half. The NSA parameter must be set to an even number.
The SNR, scan time, and spatial resolution are all maintained.
Figure 6-59 shows the Mode options.
Manual
Res
Res Res Time Time
TimeRes
(a) (b)
Figure 6-59. Mode options when Anti.aliasing is Auto (a) and Manual (b).
Size[%J- Indicates the size ofthe FOV that is measured when Anti.aliasing is
Manual. This number represents a percentage of the number entered in the
FOV parameter (under Seq. Pat-amete r). If Mode is T imeRes, Size[% ]
defaults to 200. Figure 6-60 shows the Size[% ] parameter set to 150.
Figure 6-60. Size[%] parameter option.
# RF Prep-Allows you to enter the number of reserve RF excitations prior to scanning. Th is value can affect both image contrast and artifacts.# RF P rep is
avai lable when Sequence is BASG.
DummyEcho- Aiaows the short TE signal component to be skipped when
acquiring heavily T2-weighted images. DummyEcho is available when Sequence is Prime FSE or P l"ime FIR.
Copyright@ 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 NaviEcho-Determines if the navigation echo used for compensation is
acquired. NaviEcho is automatically set to ON when Sequence is DW EPI and
Shot Num. is 2 or more.
• off- The navigation echo is acquired.
• ON- The navigation echo is acquired and compensation is implemented.
RF Phase- Allows you to enter the phase angle of the RF pulse when the RF
pulse is used to control the prev ious excitation s ignal. The unit is degrees. RF
Phase is avai lable when Sequence is BASG or PBSG. RF Phase is displayed
but unavai lable when Sequence is RSSG, TOF, PC, or RSSG EPI.
Figure 6-61 shows that Sequence is BASG, with# RF Prep set to 37 and RF
Phase set to I 17.
04 44 5 llmil Eml
Figure 6-61. RF Phase parameter example.
P hase Dir. A- Specifies the phase encoding direction for the axial (AX) plane.
Phase Dil'. A is available when Slice Plane is AX, SA, CA, or SCA. As shown
in figure 6-62, the options are:
• A-P-Sets the phase encoding direction as Anterior-Posterior.
• R-L-Sets the phase encoding direction as Right-Left.
R-L
R-L A-P
Figure 6-62. Phase Dlr. A options.
6. 41
0AS Is· MRI System Reference Manual n. htJ•t llqJMt
Note: If homogeneity of the magnetic field is poor, FatSat is vulnerable to magnetic field distortion and the fat suppression effect is lowered due to the generation of artifacts. Therefore, be sure to carry out volume shimming before performing FatSat.
Note: More echoes need to be acquired to fill the measurement space in order to acquire images with the same spatial resolution as that of Normal Scan. This results in a longer scan time than that of Normal Scan.
Note: If chemical shift occurs when using RADAR, the fat in the image may be blurred ..
6-42
Phase Dir. S -Specifies the phase encod ing direction for the sagittal (SAG)
plane. Phase Dir. S is available when Slice Plane is SAG, SA, SC, or SCA. As
shown in figu re 6-63, the options are:
• A-P-Sets the phase encod ing direction as Anterior-Posterior.
• H-F -Sets the phase encod ing direction as Head-Foot.
Figure 6-63. Phase Dir. S options.
P hase Dir. C -Specifi es the phase encoding direction for the coronal (COR)
plane. Phase Dir. C is available when Slice Plane is COR, CA, SC, or SCA. As
shown in figu re 6-64, the options are:
• R-L-Sets the phase encod ing direction as Righr-Left.
• H-F -Sets the phase encod ing direction as Head-Foot.
Figure 6-64. Phase Dir. C options.
RADAR
RADAR (RADial Acquisition Regime) is a nonorthogonal sampl ing scan
function, which samples K-space in a radial pattern. It is used to reduce motion
artifacts.
The RADAR section of the ScanParameterList window (figure 6-65) contains
the following parameters:
RADAR
'1!!'11'1
7
111 ON
M!ifil- ( Res ·J • r='404===:E=*=:*"fl ... ~ M•Fi ._124--==:E*""- *"Q~ 1§61 30 [·'·]
Figure 6-65. The RADAR section of the ScanParameterList window.
A Caution RADAR can create artifacts in the tangential and circumferential directions,
unlike artifacts that may occur with conventional scan methods. Care shou ld be
taken to avoid a potential misdiagnosis.
RADAR-Specifies whether the RADAR function is ON or off. RADAR can
be used when Sequence is FSE, FIR, primeFSE, primeFIR, SE, or BASG.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: Blade refers to a segmented area that rotates in the measurement space.
Phase
QS4-86717v3
Scan Parameters 0 Mode-Specifies measurement mode. As shown in figure 6-66, the options are;
• Res-Scan time increases while resolution is maintained.
• Time-Scan time is maintained and resolution decreases.
I'*' Re;;
Res Time
Figure 6-66. Mode options.
Proj# - Displays the total number of acquired echoes. Proj# is set
automatically, according to the value of Phase# (under Seq. Parameter).
E. Factor -Sets the number of echoes acquired per Blade. As E. Factor
increases, scan time decreases.
Blade - Disp lays the number of Blades used in the RADAR acquisition. The
system automatically calculates and displays the number of Blades, based on the
values of the Proj.# and E. Factor parameters. Blade approximates the Proj.#
value divided by the E. Factor value (Blade = Proj.# +E. Factor).
Figure 6-67 shows the relationship between Blade and E. Factor values.
E. Factor Blade Phase
Figure 6-67. The relationship between Blade and E. Factor values.
Block- Indicates the number of partitions for the entire scan. Block is available
when Sequence is BASG and Saturation is FatSat, or when Sequence is
BASG and Gating is anything but off.
Segment-Indicates the number of segments per FatSat pulse. Segment is
automatically calculated by the system using the values in the E.Factor, Blade,
and Block boxes as follows:
Segment = (Blade x E.Factor) + Block
6·43
0AS Is~ MRI System Reference Manual ThehtlentMqiMt
Note: When STIR-type fat suppression is carried out using Tl time, do not set Saturation to FatSat.
Note: If you have not set a TR value that makes the phases for water and fat opposite (around 6.8[ms]) when Saturation is PhaseCycle, the fat suppression results may be insufficient.
6-44
Saturation
The Saturation section of the ScanParameterL ist window contains the
fol lowing parameters:
Satura tion -Provides the following options for suppressing specific signals, as
shown in figure 6-68:
• off- Does not perform signal suppression.
• FatSat-Suppresses MR signals produced by fat elements by eliminating
specific RF waves. Clicking FatSat from the Saturation list also displays the
Wave, Duration, and RF amp.[% ] parameters. The maximum number that
can be set in the M ulti slice box (in the Seq. P a ra meter area) may be reduced
ifTR is to be maintained . In addition, the SNR may decrease and contrast may
change, depending on the settings for the Dura tion and Off.Freq parameters.
• Segment FS- Segmented fatsat pulse used with TIGRE sequences to
maintain fat suppression in dynamic scans.
• PhaseCycle-Scanning is performed multiple t imes and fat signals are
selectively suppressed. M ulti scan mode (in the Scan Control area) must be
set to F luoro or Dynamic and Sequence must be BASG.
• Water Excitation- Water magnetization is selectively excited and fat
magnetization is suppressed. Smaller composite pulses (that add up to 90
degrees) are used; only water protons are flipped to the transverse plane and
can emit a signal.
A Caution When Water Excitation is selected, the input range of FA changes. Check FA
and set it to an appropriate va I ue if necessary.
• Water Saturation - Particular RF waves are irradiated to suppress MR signals
emitted from water. Used only in spectroscopy (Water Saturation is
automatically selected when Sequence is MRSSE).
••"'''
A Caution
off
off FatSat PhaseCycle Water Excitation
MNSF!.
Figure 6-68. Saturation options.
off
off FatSat SegmentFS Water Excitabon
Be sure to carry out shimming before sta1ting a water excitation measurement.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Definition: Precession refers to the secondary spin of hydrogen nuclei when placed within a magnetic field.
QS4-86717v3
Scan Parameters 0 Additional Parameters when FatSat is selected
When FatSat is selected from the Saturation list, as shown in figure 6-69, the
following additional parameters are available:
Saturation
•e•11 Ad S1re
*¥"!! I '"''' Mild !I
••••
Figure 6-69. Clicking Fat Sat from the Saturation list displays additional parameters.
Wave- Provides options for the waveform of the fatsat pulse, as shown in
Figure 6-70. Each of these waveforms maintains a minimum TR, which limits
the number of s lices avai lable. H-Sinc L ight suppresses lipids. H-Sinc Heavy
suppresses lipids and fatty protons, which precess at the same frequency as
water.
AI ( s1ne r....;S;.;.;.In;.;;.e ___ -i
1-\.Sine Ught 1-\.Sine He
Figure 6-70. Wave options.
When acqu iring T2-weighted images with a large FOV, the following settings
are recommended:
• Sine- When Sequence is DW EPI
• H-Sinc Light or H-Sinc Heavy - When Sequence is FSE or Prime FSE
Dura tion - Allows the time (in milliseconds) for the fatsat pulse to be entered.
Duration determines the frequency bandwidth for the patient signal that is
suppressed by the fatsat pulse. Time and frequency bandwidth are inversely
related (for example, a shorter time results in a wider bandwidth).
RF amp.r% 1-AIIows the strength (RF amplitude) of the fatsat pulse to be
entered. If RF amp.[% J is changed, the suppression effects offat signals wi ll
change. 100% ofthe initial value is the optimal strength calculated from the
Wave and Duration parameters.
O ff.Freq[Hz)-Displays the frequency difference (in Hz) between the fat peak
and the water peak. Off.Freq!Hzl is fie ld-strength-dependent and should not be
changed. At 1.2T, the value is -173Hz. Off.F req[Hz) is unavailable when Freq.
graph is Auto or ON.
6· 45
0AS Is~ MRI System Reference Manual T'MhtJent MqHt
6-46
Segment-May be used to improve fat suppression results when Sequence is
BASG and Saturation is FatSat. In creasing the segment number divides the
fatsat pulse into segments. This may decrease scan time, but also decreases the effectiveness of the fatsat pulse.
Additional Parameters when Segment FS is selected
When Saturation is Segment FS (for use with TIGRE sequences), Wave
options include Sine and H-Sinc, as shown in figure 6-71. The recommended
wave is H-Sinc, as it provides more consistent fat suppression.
··- Sonc
Sine H-Sinc
Figure 6-71. Wave options.
Additional Parameters when Phase Cycle is selected
When Saturation is P hase Cycle, the fo llowing additional parameter is
avai lable, as shown in figure 6-72:
Quasi TimeRes- May improve time resoEution by sharing data. Quasi
T imeRes is available only when M ulti scan mode (in the Scan Control area) is
F luo ro or Dynamic.
S aturation
*"'" FIN••;• off
fr""'7:~N------.~~
Figure 6-72. Quasi TimeRes options.
Additional Parameters when Water Excitation is selected
When Saturation is Water ExciJtation, as shown in figure 6-73, the following
additional parameter is available :
Saturation
MQI!.
*II f Water Excitatoo .;:)
1-1
1- 1 1-2-1 1-3-3-1
Figure 6-73. Wave options.
Wave- Indicates the wave for the RF excitation pulse; each group of composite
pulses add up to 90 degrees. As the pulse number increases (and the tota l pulse
is longer), the water selection increases and the fat suppression effects improve;
however, the images will have more noise. The following options are available:
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 • 1-1 -One 45° pulse, one 45° pulse.
• 1-2- 1- 0ne 22.5° pulse, one 45° pulse (2x22.5°), one 22.5° pulse.
• 1-3-3-1 - One 11.25° pulse, one 33.7 5° pulse (3 x 11.25°),
one 33.75° pulse (3x 11.25°), one 11.25° pulse.
Additional Parameters when Water Saturation is selected
When Saturation is Water Saturation, the following additional parameters are
available:
Wave- Displays the water saturation pulse excitation waveform.
Water Sat BW-Sets the water saturation pulse bandwidth (ppm).
Freq. Graph Parameter
All Saturation selections include the Freq. graph parameter, which is
explained below.
Freq. graph- Determines whether or not to display a frequency graph in
the Fr·equency Prescan window, which is described in the next section. The
following options are avai lable, as shown in 6-74:
• off- Does not display the frequency graph.
• Auto - When the offset frequency for the fatsat pulse is determined in the
Exam window, that value is used during the acquisition. Auto can only be
used when Saturation is FatSat.
• ON- Displays the frequency graph.
off Auto ON
Figure 6·74. Freq. graph options.
6·47
0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
Note: Hitachi recommends using the Peak method because the Weighted method is prone to error (e.g., metal in field when the field homogeneity is distorted).
6-48
Frequency Prescan Window
The F requency Prescan window, as shown in figure 6-75, displays the
frequency graph results. This window appears at the beginning of a scan when
Freq. gra ph is ON or when F req. graph is Auto and Saturation is FatSat.
Fat peak Frequency Prescan
Water peak
Figure 6-75. The Frequency Prescan window.
This window contains the following features:
Frequency (MHz) - Displays the center frequency of water (MHz).
Offset F requency (MHz)- Represents the precessional frequency difference
(Hz) between fat and water. This value is field-strength-dependent and should
not be changed. At 1.2T, the value is -173Hz; this is the frequency of the fatsat
pulse.
Noise Threshold (%)- Used when Weighted is selected for the Search
Mode, which is described next in this section. Noise Threshold(%) allows the
threshold percentage to be selected for determining the center frequency by the
center of gravity method.
Search Mode-Allows the search method to be selected for determining
frequency values from the following options:
• Peak- Peak method, where the center frequency is set at the signal 's
maximum frequency value.
• Weighted-Center of gravity method, where the center frequency is set to the
center of gravity for signal values at or greater than the threshold.
Reset Param-Returns the values on this window to their initial settings.
CONTINUE button - Restarts the scan.
STOP button -Stops the scan.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 The graph display, as shown in figure 6-76, has the fol lowing features:
Offset frequency (fat peak)
Signal value axis
Center frequency (water peak)
Frequency (MHz) axis
Figure 6-76. Frequency Prescan window features.
• Vertical axis-Signal value
• Horizonta l axis - Frequency MHz)
• Green ve1t ical line- Offset frequency (fat peak)
• Blue vertica l line - Center frequency (wate r peak)
• Red horizontal line - Threshold when using the center of gravity method (not
shown in figure 6-76)
• Orange point - Acquisition data point (not shown in figure 6-76)
A Caution If the center frequency is changed on the graph of the frequency prescan results,
there will be an offset produced in the position of the acquisition plane. The
reference image (scanograrn) should be rescanned.
While the graph is displayed, ifprescanning is canceled using the Stop
button on the Frequency Prescan window or the Abort button on the control
panel, the frequencies that have been set will not be applied to all subsequent
acquis itions.
In addition, once the center frequency and offset frequency have been set, they
will be maintained until one of the fol lowing types of acquisitions is performed:
• Acquisition with F req. graph set to ON.
• Acquis ition with Prescan set to ON.
• Acquisition with the Exam window changed (for example, Sequence or other
parameters have been changed).
• Acquis ition with the receiver coil changed.
6· 49
0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
Note: Hitachi recommends clicking Sine from the Wave list for more uniform frequency response and better uniformity.
6-50
T2W Prep (available with CardioSuite)
T2W P rep - A prepulse that enhances the T2 contrast of the imaging target.
When T2W P rep is applied to the 3D BASG sequence with FatSat, the tissue
contrast improves but the SNR drops slightly. The available options are:
• off- T2W Prep pulses are not irradiated.
• ON - T2W Prep pulses are irradiated. When ON is selected, Duration is
displayed.
Duration -Sets the duration (in milliseconds) of the T2W Prep prepulse
application.
MTC The MTC (Magnetization Transfer Contrast) section of the ScanParameterL ist
window (figure 6-77) contains the following parameters:
MTC • '.t\fd•/.::0
Durat1on I I
RF amp [uT] I I
Off Fceq[fHz] II
Figure 6-77. The MTC section of the ScanParameterList window.
MTC- Changes the contrast of images by changing the magnetization
movement between bound water and free water. The MTC pulse is activated
prior to slice plane excitation.
Wave-Selects the waveform of the MTC pulse, as shown in figure 6-78.
[JiM Sine
Sine Gaussian
Figure 6-78. Wave options.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 Wave options are Sine and Gaussian, which differ in function as shown in
figure 6-79.
Sine function type Gaussian function type
Duration .. Duration
v~
I RF amp. 1 RF amp.
Figure 6-79. Function comparison for Wave options.
Duration - Indicates the activation time in milliseconds for the MTC pulse.
This value determines the frequency bandwidth of the MTC pulse. A shorter
duration produces a. wider frequency bandwidth and a longer duration time
produces a narrower frequency bandwidth.
RF amp.l ~tTI-Indicates the activation strength (RF amplitude) of the MTC
pulse.
Off.Freqlkzl- lndicates the offset frequency (in kHz) ofthe MTC pulse.
VENC
The VENC (Velocity Encoding) function uses phase information to acquire the
flow rate and flow direction of blood. The VENC section of the
ScanParameterList window (figure 6-80) contains the following parameters:
VENC
•• ON
16§¥ ~0 l· l:;j • II· 1
• I H-F •. ,. off
FiiiiMi! ON
Figure 6-80. The VENC section of the ScanParameterList window.
6. 51
0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
6-52
VENC-Available when Sequence is PC (Phase Contrast). When VENC is
ON, a flow encode pu lse is applied to target the blood flow.
The following parameters are available when VENC is ON:
Target Vel. - Indicates the flow rate for the target vessel in centimeters per
second. This value is a vector volume with size and direction. The value of this
parameter is the maximum val ue that can be acquired on the flow rate image;
however, flow rates that exceed the value set will be acquired as flows in the
reverse direction.
VENC Dir# - lndicates the number of axes where the flow encode pulse will
be appl ied. Provides the fol lowing options, as shown in figure 6-81:
• ! -Applies the flow encode pulse to one axis. Use the VENC Dir. parameter
(described next in this section) to select this axis.
• 3- Applies the flow encode pulse to the following three axes: the A-P axis
(front-back direction), the R-L axis (right-left direction), and the H-F axis
(body axis direction).
Figure 6-81. VENC Dir# options.
VENC Dir. -Available when VENC Did# is 1. Allows you to select the one
a,'<is to which the flow encode pulse will be applied . As shown in figure 6-82, the
options are.
• A-P- Applies the flow encode pulse to the A-P axis.
• R-L-Applies the flow encode pu lse to the R-L axis.
• H-F- Applies the flow encode pulse to the H-F axis.
Figure 6-82. VENC Dir. options.
Vel. Image- Reconstructs a flow velocity image in each axis, in add ition to the
differential combi11ation image.
Com b. Image - Reconstructs the differential combination image (angiography
image); defaults to ON. These images can be used for the MIP post-processing
task. This task is described in the "Task MTP" section of Chapter 8, " Post
Processing Tasks."
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: When a multi-slab scan is performed using SSP, the following must be considered when selecting the Rate parameter:
Since the slab is excited when sloped in the slice dtrection with SSP. the flip angle varies at the higher and lower parts. The difference of this flip angle appears as contrast.
The difference of contrast of stationary tissue appears as the edge of a step between slabs. However, the step is not always the same. and will not be prominent if Rate is low, but will be if Rate is high.
Note: Single-slab scanning is recommended with SSP.
QS4-86717v3
Scan Parameters 0 SSP The SSP section of the ScanParameterList window (figure 6-83) contains the
following parameters:
194§91111·
Figure 6-83. The SSP section of the ScanParameterList window.
SSP (Sloped Slab Profi le)-Applies an RF pulse using gradient profile
excitation to minimize the saturation of blood flow within a volume (slab).
SSP is available when Sequence is TOF and 2D/3D is 3D. Changing the RF
excitation angle inside the slab affects the spins (in the flowing blood) as they
move through the volume. A smaller angle is needed for blood entering the
volume; the angle should increase as the blood flows through the volume.
Ra te- Indicates the RF pulse ratio (slope) of inflow region to outflow region.
A larger volume demands a steeper slope, as it takes more time for blood to flow
through this larger area. The options are:
• 1.5- The ratio is 1:1.5 (smallest s lope).
• 2 - The ratio is 1:2.
• 2.5- The ratio is I :2.5.
• 3 - The ratio is I :3 (steepest slope).
Direction- Specifies the RF pulse gradient direction. Select one of the
fo llowing options to increase the RF pulse in the specified direction:
• F<H- Increases from feet to head.
• H< F -Increases from head to feet.
• R<L-Increases from right to left.
• L<R- Increases from left to right.
• A<P- Jncreases from anterior to posterior.
• P<A-Increases from posterior to anterior.
The options that can be selected for each slice plane are as follows:
• For AX- F<H and H<F
• For SAG - R<Land L<R
• For COR-A<P and P<A
Example: For the Circle of Wil lis (COW), the F< H direction would be used.
This places the smaller angle at the feet, where the blood enters the volume.
6· 53
0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
Note: Since MPG pulses are applied in Diffusion Tensor Imaging, it is sensitive to motion. In multishot measurements, to reduce artifacts due to motion. use pads to immobilize the patient as much as possible and use gating.
6-54
MPG Motion Probing Gradients (MPG) are the grad ient magnetic fields used in
diffusion weighted imaging. These grad ients are needed when imaging the
proton diffusion phenomenon. The MPG section is available when Sequence is
DWEPI.
The MPG section of the ScanParameterList window contains the following
parameters:
MPG (Motion Probing Gradient) - Specifies if the MPG function is ON or off.
MPG Dir#-Selects the number of axes to which the MPG pulse is applied.
The following options are available, as shown in figure 6-84:
• Single-Applies the MPG pulse to the A-P, R-L, or H-F axis.
• Trace-Applies the MPG pulse to the three axes in sequence.
• Tensor6- Appl ies the MPG pulse to six axes, which includes A-P, R-L, H-F,
and three obl ique directions: A-P with R-L, A-P with H-F, and H-F with R-L
(this is a purchasab le option associated with the Diffusion TensorSuite).
• Tensor7-Applies the MPG pulse to seven axes (this is a purchasable option
associated with the Tensor Suite).
• Tensor1 3 -Applies the MPG pulse to 13 axes (this is a purchasable option
associated with the Tensor Suite).
• Tensor21 - Applies the MPG pulse to 21 axes (this is a purchasable option
associated with the Tensor Suite) .
••• Single
Single Trace TensorS Tensor7 Tensor1 3 Tensor21
Figure 6-84. MPG Dir# options.
Gradient Mode- Indicates the mode to which the MPG pulse is applied. The
fo llowi ng options are provided, as shown in figure 6-85:
• Single- Applies the MPG pulse to the axis selected in MPG Dir #.
• Complex-Applies the MPG pulse to the three axes (A-P, R-L, H-F).
This parameter is unavailable when MPG Dir# is Tensor6, Tensor7, Tensor13,
or Tensor21.
IWW@M Single Single Complex
Figure 6-85. Gradient Mode options.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: Hitachi recommends using a b·factor of 1000, which is the clinical standard. Different b-factors can be used based on radiologist preference.
QS4-86717v3
Scan Parameters 0 b-factor - AIIows the b-factor of the MPG pulse to be entered. The application
time and application strength of the MPG pulse are automatically calculated
based on the b-factor value.
MPG Dir.- AIIows you to select the application axis. MPG Dit·. is available
when MPG Dir# is Single. The following options are provided, as shown in
figure 6-86:
• A-P- Applies the MPG pulse to the A-P axis.
• R-L-Applies the MPG pulse to the R-L axis.
• H-F - Applies the MPG pulse to the H-F axis.
Figure 6-86. MPG Dir. options.
Scan Control
The Scan Control section of the ScanParameterList window (figure 6-87),
contains the following parameters:
-.J . ! .. o I
WJ.Ei ,.. Every =-:::J ••••• 1
''*·II I oo oo o _, MHI§IF!~G;;;,;a;,;;,d!!!!!!!!!!!!!!!!!!!!!!~,-1 MMII o_o '4Ai!ii I oo oo o WF!QFiii ON
~----.... §I.IF!$ oft ,...:;;....--==~ 1111111@ oft ~--==~ MI!MI!I9 off ~--===-! ++M+ oft ~-=----I&F¥1 Auto
Figure 6-87. The Scan Control section of the ScanParameterList window.
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0AS Is~ MRI System Reference Manual T'MhtJent MqHt
6-56
Scan mode -Specifies the mode, if scans are to be repeated. The following
options are provided, as shown in figure 6-88:
• Once-Repeats only once.
• Discontinuous - The system asks w ith each repetition whether to perform the
scan or not.
• Every - Performs a scan the number of times equal to the value specified in
the R epeat Number parameter, described later in this section.
Once Discontir~uous
Figure 6-88. Scan mode options.
Multi scan mode-Specifies the petformance mode for the scan. The fo llowing
options are avai lable, as shown in figure 6-89:
• Normal- Performs a normal scan.
• Dynamic- Performs a scan that repeats multiple times. The time interval for
scans to be repeated can be set.
• Fluoro- Repeats a scan a number oftimes in as shott a period as possible.
During scann ing, parameters can be changed in real time.
Normal Dynamic Fluoro
Figure 6-89. Multi scan mode options.
Wait mode - Specifies the scan wait mode. The following options are
avai !able, as shown in figure 6-90:
• off-Does not pause before statting a scan.
• Auto - When Wait# is used to perform a multi-acquisition scan with multiple
breath holds, Auto enables the Auto Voice funct ion to automatically give
breath-hold instructions for each acquisition. The user does not have to press
the CONTINUE button for each acqu isition to be acquired.
• ON - Pauses before statting the scan once the prescan is finished; tim ing of
the pause is determined by the value in Wait# .
.. f off off Auto ON
Figure 6-90. Multi scan mode options.
Copyright©2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 Wait#- Indicates the number of acquisitions the system will perfonn prior to
pausing. Wait# is available when Multi scan mode is Normal or Dynamic,
Wait mode is ON, and Multi Acquisition (in the Seq. Parameter area) is 2 or
more. Wait# must be one number lower than the value in Multi Acquisition.
The fo llowing options are available:
• 0 -Scanning is perfom1ed continuous ly.
• 1- Pauses once before starting the main acquisition; the system counts the
prescan as the first acquisition.
• 2 or more- Pauses after performing two or more acquisitions, depending on
the number of acquisitions set in Multi Acquisition. For example, with Multi
Acquisition set to 5, and Wait# set to 3, the system w ill perform the prescan
and two add itional acquisitions before pausing.
After pausing, click the CONTIN UE button (figure 6-91) to resume scanning.
t·M§+d off a•·m•• ::: •
Figure 6-91. Click CONTINUE to resume scanning.
BH Time- Indicates breath-hold time per acqu isition when Wait# is not 0.
Start wait time-Sets the wait time before the scan starts. This is displayed as
minutes:seconds.tenths-of-seconds, as shown in figure 6-92. Start wait t ime is
only available when Multi scan mode is Normal and Wait mode is off.
I oo oo o
Figure 6-92. Start wait time.
Repeat Number - Specifies the number of repetitions of the scan. Repeat
Number is only available when Multi scan mode is Normal and Wait mode is
off.
No of scan set-Allows you to specify the number of scan repetitions and the
repetition interval (or wait) for each set (scans can be divided into a number of
sets with a maximum of3). No of scan set is available when Multi scan mode
is Dynamic.
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Pre-Cont. (Pre-Contrast)- Specifies the number of repetitions for the first set
of scans. Figure 6-93 indicates three repetitions for this first set.
delay time (for Pre-Cont.) - Specifies the wait time for the start of the first set.
This is displayed as minutes:seconds.tenths-of-seconds.
gap time (for Pre-Cont.)-Specifies the interval (in seconds) between
repetitions of the first set. Pre-Cont. must be set to 2 or more.
Scan#1 1st Gap Time
Scan#2 1st Gap Time
Scan#3
.. .. .. .. .. .. Individual Scan Time Individual Scan Time Individual Scan Time
Figure 6-93. Pre contrast illustration.
wait mode (for Pre-Cont.) - Prov ides the fo llowing options for the fi rst set of
repetitions:
• off- Does not pause when starting.
• Every-Pauses with each repetition. When Every is selected, gap time is hidden from view.
• Once- Pauses only for the first repetition.
After pausing, click the CONTINUE button to resume scam1ing.
Early Post Cont. (Early Post Contrast) - Specifies the number of repetitions
for the second set of scans. Early Post Cont. is available when No of scan set is
set to 2 or 3.
delay time (for Early Post Cont.) - Specifies the wa it time for the sta11 of the
second set. This is displayed as minutes:seconds.tenths-of-seconds.
gap time (for Early Post Cont.)-Specifi es the interval (in seconds) between
repetitions of the second set. Early Post Cont. must be 2 or more.
wait mode (for Early Post Cont.) - Provides the following options for the
second set of repetitions:
• off-Does not pause when sta11ing.
• Every- Pauses with each repetition. When Every is selected, gap time is
hidden from view.
• Once- Pauses on ly for the fi rst repetition.
After pausing, c lick the CONTrN UE button to resume scanning.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 Late Post Cont. (Late Post Contrast)-Allows you to specifY the number of repetitions for the third set of scans. Late Post Cont. is available when No of
scan set is set to the maximum value of3, as shown in figure 6-94.
Figure 6-94. Late Post Cont. is available when No of scan set is 3 (max. value).
delay time (for Late Post Cont.)-Specifies the wait time for the start of the
third set. This is displayed as minutes:seconds.tenths-of-seconds.
gap time (for Late Post Cont.)- Specifies the interval ( in seconds) between
repetitions of the third set. gap time is available when La1e Post Cont. is 2 or
more.
wait mode (for Late Post Cont.) - Provides the following options for the third
set of repetitions.
• off-Does not pause when sta1ting.
• Every- Pauses with each repetition. When Every is selected, gap time is hidden from view.
• Once- Pauses only for the first repetition.
After pausing, c lick the CONTIN UE button to resume scanning.
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6-60
Contrast agent-Allows a contrast agent to be specifi ed, when scanning with a
contrast agent (figure 6-95). If Multi scan mode is Dynamic, No of scan set
must be a value greater than 1 to make Contrast agent available. The list of
contrast agent options can be custom ized in the Patient Registration Setting
window. Refer to Chapter 4, "Patient Information Functions," for complete
contrast agent option list customization detai ls.
'-=o:::...ff ----L----, None Femseltz Ferric ammot>1um citrate Fendex FerumOXIdes ProHance Gadoteridol Magnev.st Meglumine gadopel\letate Gad Primovist
Figure 6-95. Contrast agent options.
Volume[ml] - Volume[ml] is available when a Contrast agent is selected. Sets
the volume of contrast agent to be used in milliliters, as shown in figure 6-96.
Gad
!2oo I· EJ
Figure 6-96. Volume[ml] example.
Travel Time- Used during contrast-enhanced magnetic resonance angiography
(CE-MRA). Enter the time it will take for contrast to arrive at the target area,
wh ich is determined from the test injection during the dynamic scan
measurement (figure 6-97).
Figure 6-97. Travel Time example.
Additional parameters displayed under Travel Time include:
OffsetTime-Used during CE-MRA. Displays the time that should be the
initial setting for the stop watch. The contrast agent is to be injected when the
stop watch reaches zero.
ContinueTime- Used during CE-MRA. Displays the timing when the contrast
agent is injected and the CONTINUE button is clicked.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 O rg. Image-Specifles whether or not to reconstruct the source images, as
shown in figure 6-98. Org. Image is available when M ulti scan mode is
Dynamic or F luoro, and Sub. I mage (described next in this section) is F ixed,
Moved , or FxMv.
ON
off ON
ON
Fe<ed
Figure 6-98. Org. Image and Sub. Image settings to reconstruct source images.
Sub. Image- Specifies the method for creating subtraction images for dynamic
scans. Sub. I mage is available when M ulti scan mode is Dyna mic or F luoro.
The following options are available, as shown in figure 6-99:
• off- Does not create a subtraction image.
• Fixed - Creates subtraction images us ing the first scan as the mask for all
subsequent scans (fixed mask).
• Moved-Creates subtraction images in which each scan uses the previous
scan as its mask (moved mask).
• FxMv- Creates both types of subtraction images: fixed and moved.
A Caution
off FIX!!d Moved FxMv
Figure 6-99. Sub. Image options.
When subtraction is performed, immobilize the patient as much as possible so
the images are as unsusceptible as possible to body movements.
The examples show how fixed and moved subtraction images are created:
Example: In fi xed subtraction, scan I is subtracted from scan 2, scan I is
subtracted from scan 3, and so on. The mask is fixed using scan I (figure 6-1 00).
Fixed-subtracts 2-1 3-1 4-1
Figure 6-100. A fixed subtraction example.
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Example: In moved subtraction, scan I is subtracted from scan 2, scan 2 is
subtracted from scan 3, and so on. The mask moves from scan to scan (figure
6-1 01).
Moved-subtracts 2-1 3-2 4-3
Figure 6-101. A moved subtraction example.
Sub. Mask Start#-Allows you to enter the number of the scan that starts the
subtraction process~ng when Multi scan mode (in the Scan Control area) is
F luoro or Dynamic. A black image (an image with all pixel values set to 0) is
output unti l the stat1 of subtraction processing. The examples show how images
are c reated when the value for this parameter is set to 3.
Example: Fixed mask subtraction, where scan 3 is the mask scan (figure 6-1 02).
Figure 6-102. Fixed mask subtraction using a Sub. Mask Start# value of 3.
Example: Moved mask subtraction where scan 3 is the fi rst mask scan (figure
6-1 03).
Figure 6-103. Moved mask subtraction using a Sub. Mask Start# value of 3.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: If moving the patient table during volume shimming correction, the shimming correction effect is lost. Therefore, movement of the patient table by the Centering option is disabled when the center of scan position is included within the volume shimming scan region. If the center of scan position is not included within the volume shimming scan region, the result of volume shimming is canceled and the patient table is moved.
Note: Static magnetic field distribution data of the volume shimming to be used in -egional shimming needs to be acquired again when moving the patient table with the Centering option.
Note: When Shading is NATURAL or when RAPID Mode is RCM, a warning message is displayed prompting you to redo the S-Map measurement if the patient table is moved approximaely 2 inches (Scm) or more by the Centering option. When aliasing artifact or nonuniformity of sensitivity occurs in a scanned image. redo the S-Map measurement.
Note: When the patient table moves long distances or to a position far from the initial positioning image for the first time. a table movement confirmation message is displayed. Confirm the safety of the patient and select CONTINUE.
QS4-86717v3
Scan Parameters 0 When M ulti scan mode is Dynamic, Sub. Mask Start# cannot be greater than
the sum of the P re-Cont., Early Post Cont., and Late Post Cont. values.
Disk save- Available when M ulti scan mode is F luoro. Provides the
following options for saving images to the database (figure 6-1 04).
• off- Only the images for which the SAVE button on the Exam window was
clicked will be saved to the database.
• ON-Saves all images to the database.
=:J· I .. i .I
Figure 6-104. Disk save options.
Table move- Provides the following options for moving the patient table, as
shown in figure 6- 1 05:
• off- Does not move the table.
• Centering - Moves the table to the center of the magnetic field, depending on
the position of the acquisition plane.
• Manual-Moves the table to the position that has been entered in the
Position lmml parameter (described next in this section).
Centenng Manual
Figure 6-105. Disk save options.
Position [mm]- Available when Table move is Manua l. Allows you to enter
the d istance of patient table movement in millimeters, as shown in figure 6-106.
Figure 6-106. The Posltion[mm] parameter.
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Note: When Auto Voice is ON. the following parameter checks and recalculations are made:
If gap time between each scan (Pre-Cont., Early Post Cont .. and Late Post Cont.) in Dynamic scan mode is shorter than the voice output time (SCANEND(Every) + SCANSTART(Every)), then gap time is recalculated. If wait mode is set to Every, delay time is recalculated.
When wait mode is off for each scan in Dynamic scan mode and delay time is shorter than the voice output time (SCANEND(Every) + SCANSTART(Every)), delay time is recalculated.
When wait mode is off for each scan in Dynamic scan mode and delay time is shorter than the SCANSTART(Once) or SCANSTART(Every) time, delay time is recalculated.
Note: When Multi scan mode is Fluoro (or Normal and Wait mode is off and a Repeat Number value is specified}, phrases are not output during each scan repetition even if SCANEND(Every) and SCANSTART(Every) are set to ON.
6. 64
Table Wait Mode-Enables/disables the patient table wait mode:
• off- Wait mode is not activated.
• ON - Wait mode is activated. Press the CONTINO E button to move the table.
Cbime (available only wben Auto Voice option is not •·egistered)- Enables/
disables the chime sound when the patient table is moved:
• off- The chime does not sound when the patient table is moved.
• ON - The chime sounds before the table is moved ..
Auto Voice-Specifies whether or not to output an auto voice pattern. The
auto voice pattern can be created in the Auto Voice Setting window, as shown
in figure 6-107. For more information about creating an auto voice pattern, see
the "Auto Voice Setting Window" section of Chapter 9, "Additional Launcher
Functions."
When Auto Voice is off, Start wait t ime (when M ulti scan mode is Normal
or F luoro) or any of the delay time text boxes (when M ulti scan mode is
Dynamic) automatically reset (display 00:00.0 instead of the minutes, seconds,
and tenths of seconds that were entered).
After creating a new auto voice pattern, you will need to close and reopen the
Exam window. Auto Voice then becomes available.
-a Auto Voice Setting
Figure 6-10 7. The Auto Voice Setting window.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: • When performing RAPID
sequences, use RAPID receiver coils.
• Some RAPID coils have a restriction on the phase encode direction available for scanning.
• The RAPID factor and direction is different for each RAPID coil.
• Image quality could be reduced if the imaging center deviates greatly from the receiver coil center.
• Image quality could be reduced if slab thickness is set to a smaller value during a RAPID sequence in the slice direction.
Note: With EPI sequence and primeFSEJprimeFIR sequence (only EchoAI/ocation is ADA). RAPID measurement makes that E.Factor decreases with Shot Num. fixed and the total scan time does not decrease.
QS4-86717v3
Scan Parameters 0 Sync. StopWa tch -Starts the timing in the StopWatch window simultaneously
with the acqu isition. Choose from the fo llowing options, as shown in figure
6-108:
• off- Does not synchronize the start of the StopWatch window with the
acquisition.
• ON-Synchron izes the start of the StopWatch window with the acquisition.
I**M•&• off ~1 1-'-o-ff -----f~
ON
Figure 6-108. Sync. StopWatch options.
Prescan- Specifies the prescan mode. Choose from the following options, as
shown in figure 6-109:
• Auto - Automatically performs appropriate prescan measurements based on
data from the previous scan.
• ON - Performs prescan measurements at the beginning of the first scan,
acquiring new data. This setting should be used on the first scan for each new
patient. ,,.,, Figure 6-109. Prescan options.
RAPID
The Rapid Acquisition through a Parallel imaging Design (RAPID) function
shortens the scan time. By using multichannel receiver coils, phase encoding is
decreased during the acquisition according to the value set in the RAPID box.
Generally, when decreasing the phase encoding for an acquisition, aliasing
is produced in the image following reconstruction. The RAPID acquisition
function acquires the data using multichannel receiver coils. It develops the
image using a sensitivity map of the receiver coils, thus e liminating alias ing
and shortening the scan time. The SNR of the image is reduced as the value of
RAPID is increased.
You cannot use RAPID unless you perfom1 an S-map that covers the imaging
region. When performing an S-map with RCM, set the imaging region so that it
sufficiently covers the area of interest. If this area is not sufficiently covered, an
error wi II occur when starting the main scan.
During S-map with RCM, a wide imaging region is captured using the T R Body
coil. Since the scanogram is performed using the RF coil, care is required so that
even regions that are not captured in the scanogram do not cause wrap artifacts.
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Note: Using ADA and RAPID results in a decrease in Echo factor per shot, so that the slice number can be increased without increasing scan time. When RAPID is utilized and Echo A/Joe. is set to ADA for EPI, Prime FSE, or Prime FIR sequences, image blurring and distortion are minimized, resulting in improved image quality.
6-66
For example: When taking images ofthe trunk of a patient 's body, the patient's
arms outside the FOV might cause wrap artifacts during S-map acqu isition.
Th is could lead to fau lty sensitivity correction in the main scan, and therefore
care is required when specifying the settings. Similarly, when taking images
of lower extremities such as the knees or upper extremities such as the e lbows,
other body areas outside the FOV might cause wrap a1tifacts during S-map
acquisition. Thi s could lead to fau lty sensitivity correction in the main scan, and
therefore care is required when specifying the settings .
Since the system is sensitive to any movement by the patient, it is important
to have the patient remain as sti ll as possible during S-map Normal mode
acquisition. To accommodate fo r patient motion such as breathing and
peristalsis, we recommend the Nest mode of the S-Map sequence.
In addition, the following precautions are required to acquire effective three
dimensional sensitivity distribution data when using S-Map:
• Specific positioning and imaging parameter settings to prevent wrap a1tifacts
in the region where the main scan is to be performed.
• Although the cross-section to be acquired depends on the area where imaging
is being performed, to avoid wrap attifacts we recommend that you select
COR or SAG, in wh ich the frequency d irection is usua lly along the axis of the
patient's body.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: Because aliasing artifact appears stronger in the center area of the image when performing RAPID scans, it is necessary to set a slightly larger FOV and to set the imaging area in the phase direction to cover the entire imaging object using the Anti.aliasing function.
QS4-86717v3
Scan Parameters 0 Figure 6-1 10 shows how the RAPID function creates images.
0 Coil sensitivity map
Aliased image
Image development anti-aliasing
Figure 6-110. Image creation using RAPID.
Resulting image
The RAPID section of the ScanPara meterList window contains the following
parameters:
RAPJD(Phase), RAPTD(Siice)-Decreases the phase and s lice encoding
in the acquisition according to the values entered, resulting in reduced scan
duration. RAPID(Pbase) and RAPID(Siice) values range from 1.0 to 4.0,
with a precision of 0.1 step. As values are entered in the RAPID(Pbase) and
RAPID(Siice) boxes, RAPID(Total) is automatically calculated and updated.
For example, when RAPID(Phase) is 1.4 and RAPID(Siice) is 1.6, RAPID(Total) will be 2.2 (the second digit to the right of the decimal poin t
is omitted). RAPID acquisition is not performed when RAPID(Phase) and
RAPJD(Siice) are both 1.0, which is the default value.
RAPID(Siice) is available when 2D/3D is 3D and Sequence is RSSG or
BASG. RAPID(Siice) is a lso available when 2D/3D is 3D, EchoTime Mode is
Optimized, and Sequence is FSE, Fffi, primeFSE, or pl"imeFSR.
RAPID(Totai) - Oisplays the product ofthe values entered in the
RAPID(Pbase) and RAPTD(Siice) boxes. This calculation is based on the
equation: RAPID(Pbase) x RAPID(Siice) = RAPID(Total).
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Note: Because the timing to acquire a coil sensitivity map is different depending on the RAPID Mode (even if the same RAPID factor is set), the reduction rates of the scan times are different.
Note: Because data for a sensitivity map is acquired during the prescan in PCM mode, the prescan time is longer than that of other modes.
Note: Because data for a sensitivity map is acquired during the main scan in SCM mode, the scan time of the main scan is longer than that of other modes. However, the prescan time is the same as that of a normal scan.
Note: RCM mode uses an S-Map to prepare the 30 sensitivity map in advance. Acquisition of a 30 sensitivity map using an S-Map under typical imaging conditions takes approximately 40 seconds.
6-68
Mode-Specifies the calibration method for the RAP ID acquisition. The
method may be selected automatically, based on the Sequence that has been
selected. The following options are available, as shown in figure 6- 111 :
• PCM (Prescan Cal ibration Method)-Acquires the coil sensitivity map during
prescan. The additional options available with this mode are described next in
this section.
• SCM (Self Calibration Method)-Acquires the coil sensitivity map during the
RAPID scan. Thi s is the default mode when certain sequences are selected.
• RCM (Reference Ca libration Mode) - Uses the sensitivity map acquired
during the S-map scan.
RCM SCM PCM
Figure 6-111. RAPID Mode options.
When Mode is PCM, the following additional parameters are available:
PCM Mode-Determines the control method for collecting a coil sensitivity
map during prescan. The default value is Auto, as shown in figure 6-112.
Figure 6-112. The PCM Mode parameter.
The following options are available, as shown in figure 6-113:
• Auto-Automatically determines whether or not to use the coil sensitivity
map collected during the previous prescan. If it can be used, reacquisition
of the coil sensitivity map is not petfonned. If there is no previous coil
sensitivity map, it is collected. Reacquisition of the sensitivity map will not
be performed ifthe following conditions are the same as during the previous
collection:
- Slice position , obl ique angle, slice interval
-Slice plane, phase direction
-Multi-slice, multi-acquisition
- FOV, reconstruction matrix
• ON-Collects a sensitivity map during each prescan.
Figure 6-113. PCM Mode options.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 PC M Wait mode-Specines whether or not to have a wait mode before
collecting a coil sensitivity map during the prescan. Choose from the fo llowing
options, as shown in figure 6-114:
• off- Does not go to standby before collecting a coi l sensitivity map.
• ON - The status changes to standby before collecting a coil sensitivity map.
l••w•M,_o_ff ___ --f off ON
Figure 6-114. PCM Wait mode options.
PC M NSA-Sets the number of signal averages when collecting the coil
sensitivity map during the prescan. The larger the value, the better the image
quality becomes; however, the prescan time is increased. The default (initial
value) is l , with a maximum value of8.
Gating
The Gating section of the ScanPara meterList window contains the following
parameters:
Gating-Allows the type of gated scan to be selected. Choose from the
following options, as shown in figure 6-115:
• off-Gated scan not selected.
• MS-ECG-Eiectrocardiograph (pu lse wave) gated scan selected.
• C ine- Cine gated scan selected.
• Resp- Respiratory gated scan selected.
Figure 6-115. Gating options.
The additional parameters that are available will vary with the type of gating
selected. the Sequence that is selected, and related scan parameters. In the
following parameter descriptions, applicable gating types are included in
parentheses after the parameter names, as shown in the example:
Example: Beat Rate (MS-ECG, Cine, Resp) indicates that the Beat Rate
parameter applies to MS-ECG, Cine, and Resp gating.
Beat Rate (MS-EC, Cine, Resp)- Enter the heart rate (in beats per minute) for
MS-ECG and Cine gating. Enter the respiratory rate for Resp gating. The heart/
respiratory rate is displayed in the WaveForm window.
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# HB Prep (C ine [ava ilable with CardioSuite])-lndicates the reserve heart rate
prior to performing the acquisition. The Gate Mode parameter (located two
parameters below# HB Prep) must be Delayed, as shown in figure 6-116.
C.ne
Figure 6-116. The # HB Prep parameter with the Delayed Gate Mode requirement
Gating Source (MS-ECG, C ine, Resp)- Indicates the signal source for the
gated scan. Se lect from the fol lowing options:
• ECG- Indicates the electrocardiograph as the signal source. ECG can be
selected when Gating is MS-ECG or C ine, as shown in figure 6-117.
• Pulse- Indicates the peripheral pulse as the signal source. P ulse can be
selected when Gating is MS-ECG or Cine, as shown in figure 6-117.
MS-ECG
ECG Pulse
Cine
ECG ECG Pulse
Gating is MS-ECG Gating is Cine
Figure 6-117. Gating Source options.
• Resp- Indicates respiration as the signal source. Resp is the fixed default
when Gating parameter is Resp.
Gate M ode (MS-ECG, Cine) - Indicates the electrocardiographic synchronous
mode. Choose from the following options, as shown in figure 6- 118:
• Gate-Gate method
• Trigger- Trigger method
• Delayed- Delayed enhanced method (available with CardioSuite)
• MyoPer-Myocardial pe1fusion method (available with CardioSuite)
Gate
Gate Trigger Delayed MyoPer
Figure 6-118. Gate Mode options.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 Resp Mode (Resp)- lndicates the respiratory synchronous mode; the fixed
default is Trigger, as shown in figure 6- I 19.
U!i&l! Tngger
Figure 6-119. The Resp Mode parameter.
Count (MS-ECG, Cine, Resp )- Indicates the number of R-wave intervals or
respiratory cycles needed to collect the desired amount of slices. The Count
value is dependent on the heart rate (a higher heart rate, with shorter R-R
intervals, requires an increased Count to obtain more slices). When Gate Mode
or Res1> Mode is Trigger, Count affects the TR. The value of I is automatically
set when Gate Mode is Gate.
Multi Phase (Cine)- Indicates the number of images to be taken at the same
position but at different heart phases. In figure 6-120, Gating is Cine and M ulti
Phase is 24.
Figure 6-120. The Mutt Phase parameter.
Segment (MS-ECG [with CardioSuite], Cine)- Indicates the segment number.
Increas ing the segment number allows less slices per R-R waveform . Segment
can be specified in the fol lowing cases, as shown in figure 6-121:
• When Gate Mode is Gate
• When Gate Mode is Trigge•· and Sequence is BASG, SARGE, or RSSG
• When Gate Mode is Delayed and Sequence is BASG
Gate Mode is Gate, Segment is 3 Gate Mode is Trigger, Segment is 3
Figure 6-121. The Segment parameter.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
6-72
DelayMode (Resp) - Indicates the input unit for Delay measurement. Select
from the fo llowing:
• Time-Sets the Delay in milliseconds (ms). The Delay represents the time
from the trigger signal to the initial sl ice TE.
• Rate-Sets the Delay as a percentage(%). The Delay represents a percentage
of the breathing cycle from the trigger signal to the TE of the initial slice.
• Min -Automatically appl ies the minimum delay time after the trigger for
image acqui sition to begin.
Delay[ms] (MS-ECG, Cine, Resp) - lndicates the time in milliseconds from the
trigger signal until the TE of the initially acqu ired sl ice.
Delay (%) (Resp)- fndicates a percentage of the breathing cycle as the delay
from the trigger signal to the TE of the initial slice.
Interval (MS-ECG, Cine, Resp) - Indicates the time interval between the
collection of each sl ice or each phase.
Echo Alloc. (MS-ECG, C ine)-AIIows se lection of the echo a llocation method.
This setting can be specifi ed in the following cases:
• When Gate Mode is Gate
• When Gate Mode is T rigger and Sequence is BASG
Choose from the following options:
• Sequential-Arranges segments sequentially.
• Centric- Arranges segments centrically. Centric is available when Sequence
is BASG (2D), BASG (3D, with Gate Mode set to Tt·igger), SARGE (2D),
RSSG, PC, TOF, or RSSG EPI.
Figure 6-122 illustrates the allocation of acquisition data for the two Echo Alloc.
methods.
Phase encoding direction
Segment#1 Segment#2 Segment#3
j Segment#4 Segment#3 Segment#2
Segment#4 Segment#1 Segment#5 Segment#1 Segment#6 Segment#2
Segment#? Segment#3 Segment#4
Sequential Centric
Figure 6-122. Allocation of acquisition data comparison for the Echo Alloc. methods.
Copyright©2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: When a gating procedure is started with Beat Rejection set to ON, use the value displayed in the WaveFonn window (the patient's heart rate) to enter in the Beat Rate box (in the Gating section of the ScanParameterList window). and don't excessively narrow the range of the regular beat.
Note: When a gating procedure is started with Beat Rejection set to ON and 16 consecutive irregular heart beats are recorded. Beat Rejection is automatically switched to off.
QS4-86717v3
Scan Parameters 0 Echo Shift-Allows the number of echo shifts to be entered. The range is
dependent on the number of segments. Figure 6-123 shows the implementation
of echo shifts.
Phase encoding direction
Segment#1
Segment#2
Segment#3 j Segment#6
Segment#1
Segment#2
Segment#3 Segment#2
Segment#1
Segment#3
Segment #3
Segment#2 Segment#4 Segment#3 Segment#1 Segment#1
Segment#5 Segment#4 Segment#2 Segment#1
Segment#6 Segment#5 Segment#3 Segment#2
Sequential/shift: 0 Sequential/shift: 1 Centric/shift: 0 C:=mtric/shift: 1
Figure 6-123. An Echo Shift illustration.
Beat Rejection- An irregular heart rhythm or pulse (arrhythmia) can cause
image quality deterioration when Gating is MS-ECG or Cine. Beat Rejection
eliminates data acquired when a1Thythmia occurs. Choose from the following
options:
• off-Data acquired when arrhythmia occurs is not e liminated.
• ON - Data acqu ired when arrhythmia occurs is eliminated. When Beat
Rejection is ON, Skip Beat, L level[%[, and H level[%] are accessible.
A Caution The beat rejection function is not effective for patients that suffer from
arrhythmia due to cardiac disease.
Skip Beat- Specifies the number of normal beats skipped after an arrhythmia.
L level[% 1- Enter the shortest regular heartbeat cycle (as a percentage of the
regular hea1tbeat cycle). The regular heartbeat cycle corresponds to the R-R
interval, which the system calculates based on Beat Rate.
H level[% 1- Enter the longest regular hea1tbeat cycle (as a percentage of the
regular hea1tbeat cycle). The regular heartbeat cycle corresponds to the R-R
interval, wh ich the system calculates based on Beat Rate.
Summary of Gating Parameters
The following table provides a summary of scan conditions and the various
parameters that are available when Gating is MS-ECG, Cine or Resp, and
instructions for how the parameters should be set.
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0AS/S~ MRI System RefeTence Manual n.. Pau ... .._
Parameters When the Gating parameter is: Available MS-ECG Cine Resp
Beat Rate Enter the heart rate Enter the heart rate Enter the respiratory rate
Indicates reserve heart rate; #HBPrep Unavailable range is 0 to 2. Gate Mode Unava ilable
must be set to Delayed 1•
Gating Specify ECG or Pulse Specify ECG or Pulse Resp
Source
Gate Mode Specify Trigger, Gate, Specify Trigger, Gate,
Unavai lable Delayed 1, or MyoPer1
• Delayed 1, or MyoPer1•
Resp Mode Unavailable Unavailable Trigger
Indicates the number of R Indicates the number of R Indicates the number of
Count waves; 1 is set if Gate Mode waves; 1 is set if Gate Mode respiratory cycles
is Gate. is Gate.
Indicates the number of Multi P hase Unavailab le images at same position, but Unavai lable
differing heart phases.
Enter a number if Gate Mode Enter a number if Gate Mode is: is: •Gate •Gate
OR OR
Segment •Trigger, with Sequence •Trigger, with Sequence
Unavailable set to BASG, SARGE, or set to BASG, SARGE, or RSSG RSSG
OR OR • Delayed!, with Sequence set • Delayed 1, with Seq uence set to BASG to BASG
Delay Mode Unavailable Unavailable Select Time (ms) or Rate (%)
Delay[ms] Indicates time from trigger Indicates time from trigger Indicates time from trigger signal to initial slice TE signal to initial slice TE signal to initial s lice TE
Enter rate(%) of breathing Delay(%) Un ava ilable Unavailable cycle from trigger signal to
TE of initial slice
Interval Indicates scan time interva l Indicates scan time interval Indicates scan time interval for each slice or phase for each slice or phase for each slice or phase
Echo Alloc.- Choose from: Choose from: Gate Mode • Sequential • Sequential must be Gate OR OR
Unavailable (or Trigger •Centr ic (with SARGE, • Centric (with SARGE, with BASG RSSG, BASG, TOF, PC, or RSSG, BASG, TOF, PC, or sequence) RSSG EPI) RSSG EPI)
Beat Unavailable
Select off or ON. If ON, enter Unavailable
Rejection a Skip Beat value.
Specifi es the number of Skip Beat Unavailab le normal beats skipped after an Unavailable
arrhythmia. 1 Available with CardioSuite.
6. 74 Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Paramete r s
Availa ble
L level[% ]
H level[%)
Note:
Scan Parameters 0 When the Gating parameter is:
M S-ECG C ine R esp
Sets a measurable range for Sets a measurable range for Sets a measurable range for trigger intervals when the beat trigger interva ls when the beat trigger intervals when the beat parameter is off. When Beat parameter is off. When Beat parameter is off. When Beat Rejection is ON, sets the R-R Rejection is ON, sets the R-R Rejection is ON, sets the R-R interval ratio for the shot1est interval ratio for the shot1est interval ratio for the shortest regular heartbeat cycle. regular heartbeat cycle. regular heartbeat cycle.
Sets the R-R interval ratio for
Unavailable the longest regular heartbeat.
Unavai lable Use when Beat Rejection is ON.
NAVI
The NaviPulse (navigator acquisition function) is an optional function used to
reduce scanning artifacts in regions (such as the heart) where the pos ition is
moved by breathing.
Navigator echo position and main scan region must be kept apart.
With this function, breathing movement is monitored by acquiring an additional
echo, called a navigator echo, from the region perpendicu lar to the diaphragm.
Using the monitored change in the position of the diaphragm, scanning
is performed with the patient "free-breathing." The s lice position can be
adjusted according to the displacement observed from the monitored breathing
movement.
QS4-86717v3
Figure 6-1 24 shows how the NaviPulse function works.
Head
I Feet
Acquisition position for navigator echo
I Breath gating for this scan I
--- I Monitoring breath movement I
Figure 6-124. Nav/Pulse illustration.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
6-76
The Navi section of the ScanParameterList window (figure 6-125), contains
the following parameters:
Figure 6-125. The Navi section of the ScanParameterList window.
NaviP ulse- Provides the fo llowing options, as shown in figure 6- 126:
• off- Does not perform navigator acquisition.
• NaviGate- Performs nav igator acqui sition.
• SlicePos-Available on ly when Sequence is BASG, performs navigator
acquisition and adjusts the sl ice position to compensate for slice variation due
to respiratory movement.
off
off NaviGate SltcePos
Figure 6-126. NaviPulse options.
GateWindow-Indicates the gate window width in mill imeters. The
acquis ition data is effective on ly when the position of the diaphragm is in the
gate window prescribed by this width. The default (initial value) is 3 mm.
Data Number·- Indicates the number of acquisition points fo r the navigator
data. The selection can be 64, 128, or 256 points, as shown in figure 6-127.
64 128 256
Figure 6-127. Data Number options.
CorrCoeff-Available when NaviPulse is SlicePos. CorrCoeff sets the ratio
of variation in slice position (due to respiratory movement) to the value of the
position adjustment. For example, if the respiratory movement detected by the
navigator mon itor is I Omm and the CorrCoeff is set to 0.6, the slice is adjusted
by 6mm.
Copyright@ 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 NaviMonitor - Indicates the method for the NaviMonitor acquisition during
the prescan. Choose from the following options, as shown in figure 6-128:
• ON-NaviMonitor acquisition is always performed prior to an acqu isition.
• Auto - In cases where the monitor acquisition has been performed for the same
acquisition, the system decides if the data is usable or not. If it is usable, the
acquisition will start without the performance of a monitor acquisition during
the prescan. If it is not usable, a NaviMonitor acquisition will be perfonned.
Figure 6-128. NaviMonitor options.
Monitor T ime- Indicates the time for the Nav iMonitor acquis ition.
PAPE
Partia l Phase Encode (PAPE) is an optional function used to improve temporal
resolution whi le maintaining the spatial resolution of the image.
The PAPE section of the ScanParameterList window (figure 6-129) contains
the fo llowing parameters:
Figure 6-129. The PAPE section of the ScanParameterList window.
PAPE- Provides the fo llowing options:
• o ff- PAPE is off.
• ON- PAPE is on.
PAPE can be set to ON when M ulti scan mode is Dynamic or F luoro, and one
of the following combinations are selected from the 2D/3D and Sequence lists:
• 2D and SARGE
• 2D and BASG
• 2D and TRSG
• 2D and RSSG
• 3D and RSSG
Scan Time- Displays time, but is unavailable. This is the time needed to
perform the acquisition, while ignoring the K-space high frequency waves.
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Note: It is recommended to set Data Rate[%] higher when scanning a region with movement.
6-78
Segment-Indicates the number of segments to be partitioned forK-space. As
the number of segments increases, the scan time per image becomes shorter,
but the update interval for high frequency data becomes longer. The selections
include 3, 5, 7, or 9.
Data Rate[% ]- Indicates the ratio for low-frequency data that will definitely
be measured(%). As this rate is increased, image quality improves but temporal
resolution degrades. The range is from 10 to 60 percent, in five percent
increments.
Scan Cycle- Displays the number of cycles. Scan Cycle is set automatically
and remains at one number lower than the setting for Segment. Scan Cycle
options include: 2, 4, 6, or 8.
Filter/PostProcessing
The Filter/PostProcessing section of the ScanParameterList window contains
the following parameters:
Org.Image-Specifies whether or not to reconstruct origina l images. Org.
Image is available when Sequence is PC (Phase Contrast). Choose from the
following options, as shown in figure 6-130:
• off- Does not reconstruct original images.
• ON - Reconstructs original images.
Figure 6-130. Org.lmage options.
Calc.lmage- Specifies whether or not to create differential images for scanned
images. Depending on the sequence selected and imaging conditions, the Calc.
Image options might not be available, might be set automatically, or may not
even be displayed. Available options are:
• off-Does not create differential images.
• Sub-Creates differential images.
• Combine- Combines data acquired with each multi echo into a single image
series. Available when Sequence is GE, SARGE, or RSSG and Multi Echo
is greater than 1.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 Image Type-Specifies the type of images to be displayed. Image Type may
be avai lable, or may be set automatically (unavailable), depending on the option
selected from the Sequence list.
The fo llowing options are available when Sequence is IR or FIR (figure 6-131 ):
• Abs-Displays absolute value images.
• Real - Displays Real images.
~····Ill 1111,._:_5_5 ___ .....,. ,
Real I Figure 6-131. /mage Type options.
The following option is automatically set when Sequence is Shim (figure 6-132):
• Phase- Displays Phase images.
QU.I· Phase
Figure 6-132. Image Type option when Sequence is Shim.
RawData Save- Avai lable to Hitachi fie ld service engineers. Specifies whether
or not to save the raw data to the database before image reconstruction. As
shown in figure 6-1 33, the options are:
• off- Does not save raw data to the database.
• ON- Saves raw data to the database.
Figure 6-133. RawData Save options.
Truncation - Filtering that can be used to reduce artifacts that may appear
when data col lection conditions allow the system to acquire fewer than the
required encoding numbers (for example, low phase encoding settings of 128 or
160). Choose from the fo llowing options, as shown in figure 6-134:
• off- Does not use the truncation fi Iter.
• ! - Applies the lightest amount of fi ltering.
• 2 - Appl ies a medium amount of filte ring, more than 1, but less than 3.
• 3 -Applies the heaviest amount offi ltering.
I ill r@i!l.i' 3 ,.._o_ff-----t
1 2 3
Figure 6-134. Truncation options.
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Note: When acquiring the S-Map data in preparation for the NATURAL option, make sure the area to be scanned is adequately covered.
6-80
Shading - Filtering that corrects for signal intensity differences throughout the
image. Choose from the following options, as shown in figure 6-135:
• off- Does not use the shad ing correction fi Iter.
• NATURAL-Uses the shad ing correction with 3D sensitivity map. It is
necessary to first acquire the 3D sensitivity map using the S-Map Sequence.
• Hybrid - When used with multiple images that are scanned in the same
position (such as with Dynamic mode), the degree of correction in the fi rst
scan is applied to later scans. When used with multiple images that are not
scanned in the same position (such as 3D scans), the degree of correction is
kept constant along the slice direction.
• Manual -Uses the shad ing correction filter. The Correction parameter
(described next in th is section) wi ll be displayed.
pn.;. NATURAL
off NATURAL Hybnd Manual
Figure 6-135. Shading options.
Correction-ind icates the intensity of the shad ing correction. The higher the
value, the stronger the correction wil l be. Correction is avai lable when Shading is NATURAL, Hybrid or Manual. The options range from Typel to TypeS
when Shading is Hybrid or Manual. The options are off, Typel or Type2 when Shading is NATURAL (figure 6-136).
4'141F' Type1
Type I Type2 Type3 Type4 Type5
(a)
163114'"·1•
{b)
off
off Type1 Type2
Figure 6-136. Correction options when Shading is (a) Hybrid or Manual and {b) NATURAL.
T2 correct.-Corrects for T2 decay that occurs with long echo train sequences.
The options are shown in figure 6-13 7.
iFF.!.!§ off
off Manual
Figure 6-137. T2 correct. options.
Copyright©2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: When Sequence is isoFSE. T2 correct. is automatically set to Manual and T2 Target is no longer available. Only Level[%] can be set.
QS4-86717v3
Scan Param e ters 0 Leveii% 1- Sets the level of the T2 Amplitude Correction Filter, The larger the
value, the stronger the correction. L evel[% ] is available when T 2 correct. is
Manua l (figure 6-138).
;*i'i"'i§3iii[ Manual IMII [3§11 °oo1 ___l = ~ ~ J IMI!i!i [iOo"" =r -I -1
Figure 6-138. Level[%] and T2 Target parameters.
T2 Target-Sets the T2 value for the T2 amplitude correction area. T2 Target
is available when T2 correct. is M a nual (figure 6-138). T2 Ta rget should be
set to match the TE value.
Ad a ptive F ilter - Performs fi Iter processing for the scanned image (figure
6-139). For more adaptive fi Iter information, refer to the "Review Task
Window'· section of Chapter 7, "Review and Fi lming Functions".
•••!§ lloff ~ II off SmiShO Sm1Sh1 Sm1Sh2 Sm2Sh0 Sm2Sh1 Sm2Sh2 Sm3Sh0 Sm3Sh1 Sm3Sh2 Sm4Sh0 Sm4Sh1 Sm4Sh2 M1n Med Max MRAM1n MRAMax
Figure 6-139. Adaptive Filter options.
Ed ge enhance- Performs edge enhancement for the scanned image. For more
edge enhancement information, refer to the ··Review Task Window" section of
Chapter 7, " Review and Filming Functions''.
MIP I mage- Specifies whether or not to create MTP reference images
automatically after the scan is finished. Choose from the following options, as
shown in figure 6-140:
• ofT- Does not create MIP reference images.
• ON-Creates MlP reference images automatically after d1e scan is finished.
~~l,lil41'819111111~o_N ______ ~~~
I ~N j
Figure 6-140. MIP Image options.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
Note: When Diffusion Analysis is ON, the DW EPI sequence is vulnerable to magnetic field distortion. If homogeneity of the magnetic field is poor, image degradation and artifacts may occur. To reduce this effect, be sure to carry out volume shimming before starting Diffusion Tensor Imaging.
6-82
When MIP Image is ON, the following parameters become available:
MIP Edge Enh.- Adjusts the quality of the MIP reference images that are
created. The adjustment range is from -5 to 5. The image smoothness increases
as it approaches -5, and the image sharpness increases as it approaches 5.
MlP Dir.-Selects the view direction ofMIP reference images. Choose from
the following options, as shown in figure 6-141:
• front-Creates MIP reference images viewed from the same direction as the
direction set in Slice P lane.
• AX-Creates MIP reference images viewed from the axial direction.
• COR-Creates MI P reference images viewed from the corona l direction.
• SAG-Creates MIP reference images viewed from the sagittal direction.
• SA-Creates MIP reference images viewed from the sagittal and axial directions.
• CA- Creates MIP reference images viewed from the coronal and axial directions.
• SC-Creates MIP reference images viewed from the sagittal and coronal directions.
• SCA-Creates MIP reference images viewed from the sagittal, coronal, and
axial directions.
@iii AX 1-fr- o-nt----{
AX COR SAG SA CA sc SCA
Figure 6-141. MIP Dir. options.
For more information about MIP reference images, refer to the "Task MIP"
section of Chapter 8, "Post-Processing Functions."
Diffusion Analysis-Specifies whether or not to create diffusion analysis
images automatically after the scan is fi nished. Diffusion Analysis is available
only when Sequence is DW EPI. Choose from the following options:
• off- Does not create diffusion analysis images automatically.
• ON - Creates diffusion analysis images automatically after the scan is
finished.
When Diffusion Analysis is ON, the following parameters become available:
ADC -Available when MPG Dir# is Single or Trace. If Single is selected,
ADC defaults to ON. IfTrace is selected, the fo llowing options become
available:
• off-ADC images are not created automatically after scanning.
• ON - ADC images are created automatically after scann ing.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: The b-factor value summarizes the influence of the gradients in OWl. The higher the b-factor value. the stronger the diffusion weighting. Hitachi recommends a b-factor of 1000.
QS4-86717v3
Scan Parameters 0 DWI trace- Avai lable when MPG Did# is T race, Tensor6, Tensor7,
Tensor13, or Tens01·21 (optional). Choose from the following options, as shown
in figure 6-142:
• off-DWI trace images are not created automatically after scanning.
• ON (with bO) - DWI trace images are created automatically after scanningj
including bO image.
• ON (without bO) - DWI images are created automatically after scanning,
without bO images.
I'"""' ON(without bO) •
off ON(wrth bO) ON(wrthout bO)
Figure 6-142. DWI trace options.
FA (Fractional Anisotropy)- (Associated with the Diffusion TensorSuite,
which is a purchasable option.) Available when MPG Dir# is Tensor6,
Tensor7, Tensorl 3, or Tensor21. Calculates an index FA showing the
anisotropy of diffus ion from the obtained diffusion tensor, and creates an FA
map reflecting an FA value. The options are:
• off- FA images a re not created automatically after scanning.
• ON - FA images are created automatically after scanning.
MD ( Mean Diffusibi lity)- (Associated with the Diffusion TensorSuite, wh ich
is a purchasable option.) Available when MPG Dir# is Tensor6, Tensor7,
Tensor13, or Tensot·21. Calculates the mean of the intrinsic values of
diffusibility and creates an image reflecting the MD. The options are:
• off- MD images are not created automatically after scanning.
• ON-MD images are created automatically after scann ing.
Figure 6-143 shows the FA and MD parameters.
l§liiYY@Wr oN ••;;;
Figure 6-143. FA and MD parameters.
Save Corr.lmage- When Save Corr.Image is ON, the original images and the
distortion-corrected images are saved in the system database. When Save Corr.
Image is off, the corrected images are not created automatically after scanning.
Noise T bresbold- lndicates a threshold value to eliminate background noise.
The range is 0 to 100; increasing the value e liminates more noise.
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0AS Is~ MRI System Reference Manual T'MhtJent MqHt
Note: Distortion correction settings will vary depending on the body part being scanned.
6-84
Correct Distortion - Specifies whether or not to correct distortion of the input
image. The options are:
• off- Image distortion is not corrected for the FA map, MD map, and OWl
Trace images.
• ON- Image distortion is corrected for the FA map, MD map, and DWI Trace
rmages.
D.C.Levei-Corrects image distmtion generated by nonlinearity in the gradient
magnetic field. The options are:
• off- Image dist01tion is not corrected.
• Auto- The system applies distorttion correction as needed.
• GC-(Grad ient Correction) Distomtion correction is always applied.
When D.C.Level is Auto or GC, Region Cut is displayed.
Region Cut- Regitons that cannot be corrected by the distortion correction
funct ion may appear on the edge oftlhe image. Region Cut options (as follows)
determine whether or not the uncorrected regions aTe cut from the image:
• off- The regions are not cut from the image. This is the recommended option
when scanning large anatomical regions (such as large abdomens), to ensure
that a ll of the anatomy of interest is inc luded.
• Auto- The regions are cut fi·om the image when there are regions that cannot
be corrected by the distortion correction function.
W-Widtbl - Indicates the window width of the display for one echo. The set
value becomes the default window width for displaying images. After an image
is displayed, the window width can be changed.
W-Levell - lndicates the window level of the display for one echo. The set
value becomes the default window level for displaying images. After an image
is displayed, the window level can be changed.
W-Widtb2- Available when Multi Echo (in the Seq. Parameter area) is 2 or
greater. Indicates the window width of the display for two echoes. This value
becomes the default window width for displaying images. After an image is
displayed, the window width can be <:hanged.
W-Levei2 -Available when M ulti Echo (in the Seq. Parametea· area) is 2 or
greater. Indicates the window level of the display for two echoes. This value
becomes the default window level for displaying images. After an image is
displayed, the window level can be changed.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 Figure 6-144 shows the window width and level parameters.
Wijd
••• WI!!
MM'
Figure 6-144. Window width and window level parameters.
Positioning
Positioning parameters allow you to select various options involved with the
scanning and viewing of images.
The Positioning section of the ScanParameterList window (figure 6-145)
contains the fo llowing parameters:
Figure 6-145. The Positioning section of the ScanParameterList window.
Slice Ord. A- Specifies the direction in which the axial plane slices wi ll be
scanned and displayed. Choose from the following options, as shown in ·figure
6-146:
• H-F- From head to feet
• F-H- From feet to head
81&14
Figure 6-146. Slice Ord. A options.
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Note: Plane Order cannot be changed, but the slice order within a plane can be.
6-86
Slice Ord. S-Specifies the direction in which the sagittal plane s lices wi ll be
scanned and displayed. Choose from the following options, as shown in figure
6-1 47:
• R-L-From right to left
• L- R-From left to right
Figure 6-147. Slice Ord. S options.
Slice Ord. C -Specifies the direction in which the coronal plane slices will be
scanned and disp layed. Choose from the following options, as shown in figure
6-148:
• A-P-From anterior to posterior
• P-A- From posterior to anterior
Figure 6-148. Slice Ord. C options.
Plane O•·der -Displays the scanning order of the slice planes. Plane Order is fo r display only, it cannot be changed.
The following planes are available for display:
• AX-Axial plane
• SAG -Sagittal plane
• COR-Coronal plane
• S-A- Sagittal plane, axial plane
• S-C-Sagittal plane, coronal plane
• C-A- Coronal plane, axial plane
• S-C-A-Sagittal pane, coronal plane, axial plane
Figure 6- 149 shows a Plane Order of S-C-A.
IM§i§ S-C-A
Figure 6-149. The Plane Order parameter.
Copyright©2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 Radial Sta ck-Allows easier radial slice stack positioning for MRC P
exams. When Radia l Stack is ON, the radia l stacks move as a group, making
positioning at a central point easier.
To use radial stack positioning, make sure Radia l Stack is ON, then enter the
number of radial stacks to be performed in the Stacks box (located in the Seq.
Para meter area of the ScanParameterList window).
Slice Alloca tion- Ind icates the order of slice excitation for multi-slice
scanning. Slice Allocation is available when:
• 2D/3D is 2D
• Sequence is GE, SAR GE, or RSSG
• The Mode parameter of M ulti Acquisition is Interleaved
As shown in figure 6-150, Slice Allocation options include:
• Default-Scans from one s ide of the s lices to the other side.
• Convergence-Scans from both s ides of the s lices towards the cente r.
HMIM!iii+ (....,;o;;...;;e....;..tau....;..lt __ --4·1 Default I Converpenc~
Figure 6-150. Slice Allocation options.
Line/Box-Specifies the manner in which 20 imaging s lice lines appear when
they are displayed in d1e viewports for positioning. L ine/Box is not displayed
when 3D is selected from the 2D/3D box. The following options are available,
as shown in figure 6-15 I:
• Line- Displays the slice surface as a line.
• Box- Displays the slice surface as a box.
iii§. Une ~.;;...._------i
L1ne Box
Figure 6-151. Line/Box options.
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Guide L ine -Specifies whether or not guidelines will appear when changing
slice position or number of slices. Guidelines are the dotted lines displayed at
the top and bottom of the slice group. The following options are available:
• Yes- The dotted lines are longer than the sl ice lines and continue to be
displayed when s lices are moved. Figure 6-152 shows the results when Guide
Line is Yes.
Figure 6-152. The Guide Line parameter set to Yes.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 • No- The dotted lines are approximately the same length as the slice lines and
are displayed around the outer edges of the s lice group. The dotted lines will
e longate and display during s lice movement. Figure 6-153 shows the results
when Guide Line is No.
Figure 6-153. The Guide Line parameter set to No.
G.Intvl-Specifies whether or not the slice interval can be changed for each
s lice stack or slab group for scans that involve multiple stacks or slabs. The
following options are avai lable, as shown in figures 6-154 and 6-155:
• off- The slice interval for each slice or slab group can be changed. When
G.lntvl is off, the lntet'Val box is displayed in the Scan Positioning
Information bar at the bottom of the Task View area. Figure 6-154 shows the
G.Intvl parameter set to off.
I'IMI¥··· 1._ott ____ _.·l
Figure 6-154. G.Jntvl set to off.
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0AS Is-MRI System Reference Manual YbehtJ ... tlilqHt
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• ON - The slice intervals for each slice or slab group are set to the same value
and cannot be changed individually. When G.Intvl is ON, Interval is
displayed in the Seq. Parameter area of the ScanParameterList window.
Figure 6-155 shows the G.Intvl parameter set to ON.
iip ON '------.J
Figure 6-155. G.lntvl set to ON.
Sync.-Specifi es whether to simultaneously change all plane settings when the
settings for position , angle, and slice number are changed, and multiple planes
have been selected. Sync. is available only when Slice Plane is SA, SC, CA, or
SCA. Choose from the fo llowing options, as shown in figure 6-156:
• off-Does not change the settings of a ll planes.
• ON-Changes the settings of a ll planes.
Others
I iii! off
off ON
Figure 6-156. Sync. options.
The Others section of the ScanParameterList window contains the following
parameters:
Receiver Coil-Select the receiver coil name from the list of connectable
receiver coils, as shown in figure 6-157. If Receiver Coil is Auto, the receiver
co il name is recognized automatically.
Auto CTL Large Joint PI/ 00 Flex Body(L) 00 Flex Body(XL) OOHead RAPID Body RAPID Breast RAPID C-Spine RAPID Foot RAPID Head RAPID Knee RAPID NV RAPID Shoulder RAPID Wrist TR
Figure 6-157. Receiver Coil options.
Copyright© 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
QS4-86717v3
Scan Parameters 0 Mode-Specifies the receiver coil mode for multi-mode coils, such as the CTL
and RAPID Foot coils. A mode can be selected from the Mode list that is
available for the receiver coil chosen from the Receiver Coil list, as shown in
figure 6-1 58.
IB'di*IHI*I'I"IIr RAPtDFoot lj8MI I 811 Ext Full 811 Ext Full Bit Ext Full Lt 811 Ext Full Rt 811 Ext Foot 8~ Ext Foot Lt 8il Ext Foot Rt
41
Figure 6-158. Mode options.
CTLC CTLCT CTL T CTLL CTL C-No Loop CTL CT-No Loop CTL T-No Loop CTL L-No Loop
If Receiver Coil is Auto, Mode changes to Auto, as shown in figure 6-159. The
system will set the most common mode for the receiver coil that is being used.
Figure 6-159. Mode is Auto when Receiver Coil is Auto.
MorningQA-Specifies checks to be petformed during the morning quality
assurance (QA) procedure. When starting the system, scanning is performed
with fixed parameters to confirm that the system is operating correctly. All
parameters that are currently set are disabled, and the fixed parameters are set.
Choose from the fo llowing options, as shown in figure 6-160:
• off- Does not perform Morn ingQA.
• GC Check - Fl D- Acquires the FID (free induction decay) s ignal.
• GC Check- X-Checks X-axis grad ient movement.
• GC Check - Y - Checks Y-axis gradient movement.
• GC Check - Z-Checks Z-axis gradient movement.
• Coil Check- Checks each channel of the coil.
ii@idl&lfl ,._o_ff ____ -f off GC Check- FID GCCheck-X GCCheck- Y GCCheck- Z Co1ICheck
Figure 6-160. Morning OA options.
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0AS Is~ MRI System Reference Manual T'MhtJent MqHt
Note: The TIGRE measurement sequence is a fat-suppression imaging method using a fatsat pulse. To obtain the high tatsuppression effect, homogeneity of the static magnetid field is important. Therefore, be sure to carry out volume shimming prior to performing TIGRE sequence scan. Utilizing the regional shimming function (available as an option) together with volume shim data can provide consistent fat suppression.
Note: With a 30 acquistion, the SNR of the images at the top and bottom edges of the slab is lower compared to that at the center region. Therefore, position the region of interest at the center of the slab and set the number of slice encodes to a slightly higher value.
Note: Hitachi recommends Circular 3D Acq. Mode with TPEAKS Echo Alloc. for all TIGRE acquisitions.
6-92
Soft Sound- Specifies the Soft Sound mode, which decreases the noise level
for certain pulse sequences. Activation ofthe Soft Sound mode requires an
increase in TR, and, consequently, an increase in scan time. Choose from the
follo·wing options, as shown in figure 6-161:
• off- Acquisition is not performed in Soft Sound mode.
• ON -Acquisition is performed in Soft Sound mode.
[11!11.1 off . 11 off ON
Figure 6-161. Soft Sound options.
TIGRE
The TIGRE sequence is a 3D fast, TI-weighted, RF-spoi led SARGE sequence
using a fatsat pulse. This sequence can be used forT L -weighted, fat-suppressed,
dynamic imaging with contrast. A segmented fatsat pulse is used to maintain
fat suppression and provide sufficient temporal resolution for dynamic scans.
Shimming must be performed before the TIGRE acquisition.
The specific parameter selections that are required or recommended for TIGRE
are described below.
Sequence Area
Select the following:
• 2D/3D-Select 3D.
• Sequence-Select RSSG.
Seq. Parameter Area • Echo Alloc.-Select either Cent-Cent or Cent-Seq, as shown in figure
6-162:
Cent-Cent- Echo allocation for phase encode and slice encode directions
are both Centric. The #RF Prep value should be increased (as compared
to the Cent-Seq value) to suppress artifacts, even though th is reduces the
effects of fat suppression.
Cent-Seq - Echo a llocation for the phase encode direction is Centric,
wh ile echo allocation for the sl ice encode direction is Sequential.
IW!iii (Cent-Cent Cent-Cent
I Cent-Seq
IMNI.I TPEAKS
- ('"c-irc_u_la-r -..=....::..::;· )
Figure 6-162. Seq. Parameter area settings.
Copyright@ 2012 by Hitachi Medical Systems America, Inc. All rights reserved.
Note: When 3D Acq. Mode is Circular. Slice# and Segment may be restricted.
Note: If Segment is set to an extremetly large value, longitudinal magnetization of fat is recovered and the fat suppression effect may be reduced.
Note: Make sure to carry out volume shimming before performing the 1.1 TE scan. If homogeneity of the magnetic field is poor, 1.1 TE is vulnerable to magnetic field distortion and degraded image quality due to the generation of artifacts. The scan should be
within the center of the magnetic field as much as possible.
Note: When performing a 1.1 TE scan, a coil or pad may appear in the image.
Note: The 1.1 TE scan is designed to acquire a weighted image, not appropriate for T2 value calculation.
QS4-86717v3
Scan Parameters 0 • 3D Acq. Mode- When Cil·cula r is selected, Echo Alloc. is TPEAKS and the
outer corners of K-space are not acquired, which reduces scan time.
Advanced Area For #RF Prep, Hitachi recommends using a value of about 5 when Echo Alloc.
is Cent-Seq, or a value higher than that when Echo AUoc. is Cent-Cent. This
value represents the number of dummy RF pulses needed to maintain the steady
state after the application of the segmented fatsat pulse. Larger numbers may
improve artifact suppression but also reduce the effect of fat suppression.
Saturation Area Select the fo llowing, as shown in figure 6-163:
• Saturation-Select Segment FS.
• Wave- Select H-Sinc.
• RF amp.[%]- Enter 100.
• Segment- Hitachi recommends a value of about 32.
Saturation
**"·'
Figure 6-163. Saturation area settings.
Additional Notes and Cautions for the 11TE pa r·ameter :
IL Caution Use the RAPID knee coil for 11TE measurements. If any other coils are used,
image quality can be subpar.
A Caution Images may be blurred because the bandwidth is low. The T2 attentuation occurs
due to the extension of sampling time.
A Caution Image quality (image formation) may be altered when the parameters associated
with readout gradient strength, such as FOV, Bandwidth, or Oblique, are
changed.
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0AS Is· MRI System Reference Manual T1MI htJ•t llqJMt
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Additional F luoroscopy Notes a nd Cautions:
A Caution The scan time displayed does not always coincide with the fluoroscopy image
when displaying the latest images.
A Caution If multi-slice imaging is performed, images are not displayed until all slice data
is obtained.
A Caution When scan time is shorter than reconstruction time, data scanned during
reconstruction may not be displayed or saved.
Copyright@ 2012 by Hitachi Medical Systems America, Inc. All rights reserved.