case study | advanced apps on open deser… · standard for detecting prostate cancer, trus biopsy...

© 2014 Hitachi Medical Systems America, Inc. All rights reserved.

OASIS 1.2T: MULTIPARAMETRIC MRI OF PROSTATE CANCER

Case Study | Advanced Apps on Open

By Dr. John Feller, MD, RadiologistDesert Medical Imaging, Palm Springs, CA



MRI is clinically accepted as the best imaging modality

for displaying anatomical details of the prostate, and has

been a valuable diagnostic tool for aiding the detection

and localization of prostate cancer. Prostate MR is often

incorporated into the clinical workup as a staging tool after

a diagnosis is made through trans-rectal ultrasound (TRUS)

biopsy to exclude extension or metastasis of cancer outside

the prostate gland. Despite being recognized as the gold

standard for detecting prostate cancer, TRUS biopsy misses

30-35% of prostate cancers with abnormally high PSA levels

or a positive digital rectal exam - a high false negative rate

that complicates the decision path for the Urologist.

In addition, in respect to prostate cancer it does diagnose,

TRUS biopsy under-grades Gleason scores 35-45% of

the time.

Recently, MRI has offered a promising new implementation

for prostate cancer diagnosis and intervention through the

use of multiparametric techniques as an alternative to TRUS

or patients with negative TRUS-guided biopsies.

• Diffusion-weighted imaging (DWI) allowing for better

assessment of prostate cancer aggressiveness through

inverse correlation with low, intermediate, and high

Gleason scores.

• Dynamic contrast-enhanced (DCE) imaging shows

promise for better characterizing prostate cancer.

• Combined contrast methods to improve detection and

localization of prostate cancer for targeting lesions for

either biopsy or minimally invasive surgical procedures.

Multiparametric imaging of the prostate using the OASIS

1.2Topenhigh-fieldplatformallowsathoroughdiagnostic

workup to fully assess structural and functional detail. The

opendesignaddsnotonlythecommonlyunderstoodbenefit

ofpatientcomfortandaccessibility,butalsotheflexibility

for patient and interventional device positioning to enhance

the access and results of the biopsy. Leveraging current

Body coils, OASIS can achieve acceptable performance

characteristics of prostate cancer detection and localization

comparedto1.5Tand3.0Tfieldstrengths,allowingmore

imaging options for the Radiologist and the patient.

Patient History

A 73-year-old male presented with elevated serum PSA

levels (11) and symptoms including the urgency to urinate.

The patient had a history of benign prostate hyperplasia

(BPH), or enlargement of the prostate, but no obstructive

urinaryflowsymptoms.Thepatienthadalsoreceivedtwo

negative TRUS biopsies. MRI was performed to evaluate for

prostate cancer and the potential for MR guided biopsy of the

prostate gland.

John Feller, MDBoardcertifiedRadiologistwith

Desert Medical Imaging and leading

global advocate for the advancement

of Prostate MR


MR Imaging Technique

A number of different pulse sequences are currently used

in our clinical practice for diagnostic prostate cancer MR

exams using a RAPID Body 6ch receiver coil. Table 1

details our sequences and general parameters for T1-

weighted imaging (T1WI), T2-weighted imaging (T2WI),

diffusion weighted imaging (DWI), and dynamic contrast

enhanced imaging (DCE), each playing a role in the

assessment of the glandular zones of the prostate (central,

peripheral,transition,anteriorfibro-muscular)andadjacent

tissue structures (seminal vesicle, urinary bladder,

osseous structures).

T1 Weighted Imaging

Unlike T2WI, T1WI is generally not helpful for contrasting

diseased from healthy tissue. The primary reason for

acquiring T1WI is for the determination of the presence and

location of hemorrhage. T1WI can contrast blood products

occurring as a consequence of biopsy sampling, where

areas of hemorrhage appear as hyperintense regions on

Figure 1 - T1 FSE axial acquisition depicts no evidence of blood products / hemorrhage

Acquisition Plane TR (msec)

TE (msec)

Thick (mm)

FOV (cm)

Matrix Other Settings

Scan Time

FSE – T1 Axial 450 10 4.0 20 256x208 4:12

FSE – T2

Axial 5700 96 4.0 20 256x704 RADAR 5:37

Coronal 5693 96 4.0 20 256x704 RADAR 5:14

Sagittal 5700 96 4.0 20 257x704 RADAR 5:37

DWIAxial 1900 62 4.0 28 96x96 B – 100 1:36Axial 1900 62 4.0 28 96x96 B – 800 2:06Axial 1900 62 4.0 28 96x96 B – 1000 2:06

3D DCE – T1 Axial 4.3 2.2 4.0 22 120x108Post gad

performing 40 acquistions

0:10 (7:57 total)

TR–Repetitiontime,TE–echotime,FOV–fieldofview

Table 1 - Details of Our Prostate Cancer Staging MR Examination as Implemented on a 1.2T Scanner (Hitachi Medical Systems America)

T1WI due to the shortening of T1 caused by blood. When

hypointensities appear on T2W images that are suggestive

of cancer, T1W images should be evaluated to rule out

hemorrhage if there is a history of prior prostate biopsy.

Using a classic fast-spin echo (FSE) with a small FOV

(< 30), the patient scan showed very little contrast between

tissues, indicating little to no hemorrhaging effects from prior

TRUS biopsies.



T2 Weighted Imaging

T2WI is captured using FSE in the three orthogonal planes

(axial, sagittal, coronal) typically resulting in excellent T2

contrast for the depiction of zonal anatomy, including the

peripheral zone (PZ), central zone (CZ), and transition

zone (TZ). Imaging is done using repetition time (TR) of

5.7 seconds, effective echo times of 96 msec, small 20cm

FOV, 4mm slice thickness, and in-plane matrices of 256

X 704 deploying a radial acquisition motion compensation

technique (RADAR). Though radial acquisition techniques

add acquisition time, motion compensation is important to

implement to reduce potential artifacts from involuntary bowel

and bladder wall motion.

For our patient, T2WI showed inhomogeneous signal

intensity through the TZ associated with nodular enlargement

mostcommonlyduetoBPH(Figure2a-2b).Ill-definedT2

shortening is evident in the TZ, indicating a tumor suspicious

region far anteriorly in the midline at the base and mid

gland levels that extends to the left into the right of midline

measuring 1.3cm X 1.8cm X 2.6cm. The left PZ posteriorly

to the apex also shows T2 shortening effects. However,

in reviewing the sagittal acquisition (Figure 2d) which is

the most useful for evaluating seminal vesicle invasion,

there was no evidence of tumor progression, most likely

indicatingfibrosis.

Diffusion Weighted Imaging

One of the more important recent advances in prostate cancer

imagingistheuseofapparentdiffusioncoefficient(ADC)

values derived from diffusion weighted imaging (DWI) for

characterizing prostate tissue. With the onset of neoplasia,

the diffusion capacity of water molecules is diminished. DWI

measures the water diffusion within tissue, helping improve

the contrast between cancer and normal parenchyma. When

combinedwithT2WI,DWIdramaticallyimprovesspecificityin

prostate cancer detection.

Figure2-T2FSEwithRADARmotioncompensationwereacquiredreflectingprostate gland measurements of 5.0cm X 5.4cm x 6.1cm captured in axial (a) and sagittal (b) images, consistent with a highly enlarged prostatic gland volume of 86cc.


Figures 2(c) and 2(d) indicate tumor suspicious region measuring 1.3cm x 1.8cm x 2.6cm in the far anterior TZ.

With our DWI, we sample each slice within the 28cm FOV

with a b-value of 100, 800, and 1000 s/mm2. The b-value

of 100 is used to show the combination of DWI and T2WI

information, with higher b-values of 800 and 1000 showing

DWI effects alone, each in relatively short acquisition times

of 2:06. Combining b-value trace images with the baseline

(b-value 0) allows for calculation of the ADC image, known

also as the ADC map. The ADC map is free of all T1, T2, and

receiver coil sensitivities, and quantitative measurements of

tissue water diffusion may be made from individual voxels, or

regions-of-interest (ROIs).

a b

c d


Figure 3 – (a) High b-value 1000 DWI trace depicts a hyperintense dominant tumor suspicious region while the corresponding ADC map (b) demonstrates restricted diffusion areas indicated by the hypointense lesion (dark) in the same region.

Dynamic Contrast Enhanced Imaging

The goal of dynamic contrast enhanced (DCE) imaging is to

capture the passage of contrast material into and out of the

prostate using T1WI with high temporal resolution (between

5–10 sec). DCE imaging acquires data on tissue perfusion

characteristics and tumor wash-in / wash-out contrast to look

for increased angiogenesis in suspected tumors.

On OASIS, we accomplish this using a dynamic T1 weighted

3D RSSG protocol using very short TR periods of 4.3msec,

flipangleof15,andslicethicknessof4.0mm,whichacquires

120 X 108 X 256 3D matrix data at 10 second intervals

with parallel imaging factors of 1.5. We generally perform

about 40 such acquisitions consecutively, with gadolinium

(Gd) contrast automatically infused following 1 precontrast

baseline acquisition. The overall acquisition time took

approximately 7:57.

In this patient, you can see evidence of restricted diffusion in

the high b-value (1000) DWI trace and ADC map (Figure 3)

shown in the same area as the T1WI and T2WI acquisitions.

TheDWItracewithb-valueof1000clearlyreflectsa

hyperintensity in the suspected region, while the resulting

ADC map show lower ADCs (hypointense or darker) than the

surrounding healthy prostate tissue.

For our patient, the resulting DCE image acquisitions allow us to generate signal versus time kinetic curves from selected ROIs that adequately characterize the signal changes accompanying the distribution of the Gd contrast agent over the entire prostate gland. The temporal resolution of typical DCE acquisitions is fast enough to capture the rapid increaseofsignal,orwash-inphase,occurringwithinthefirst60 seconds of contrast administration as noted by the 450% enhancement peak (Figure 4). The temporal resolution is also sufficienttoallowforaquantitativeassessmentoftheratethat this signal enhances from the initial slope of the signal versus time curves. The 3D RSSG imaging data set is then transmitted to a dedicated computer-aided detection (CAD) and 3D workstation where additional 3D images were reconstructed.

a b

Figure 4 –DCE acquisitions show (a) 450% peak enhancement with a rapid wash-out kinetic curve pattern (b) correlating to region of interest color overlay in axial image.

a

b



Diagnostic MR Findings

UsingT2WIalone,findingseffectivelyindicatednodularenlargement in the CZ most commonly due to BPH and a tumor suspicious region. However, by leveraging a broader Multiparametric Prostate MR protocol, we were able to combine findingsfromDWIandDCEtechniquesthatsignificantlyimproveprostate cancer sensitivity and the negative predictive value

(NPV) compared to T2WI alone.

Our diagnosis concluded that while there was no evidence of extracapsular extension, seminal vesicle invasion, or periprostatic lymphadenopathy, the TZ demonstrated characteristicssuggestiveofprostatecancerincludingill-definedT2 shortening, evidence of restricted diffusion, and a rapid washout pattern of dynamic gadolinium contrast enhancement indicating increased vascular permeability. As a result, we recommended MR targeted biopsy of the prostate gland.

MR Guided Prostate Biopsy Technique

The patient returned for the follow-up biopsy 8 weeks later to be conducted on the OASIS 1.2T MR system with a Body Flex XL receiver coil. MR guided biopsy was performed utilizing Invivo Prostate DynaCAD and DynaTRIM hardware and software.

The patient was placed on the MRI table in the prone position and conscious sedation was performed at the start of the procedure. The needle sleeve biopsy guide was placed in the rectum with the DynaTRIM localization device attached to the biopsy guide. Preliminary sequences were obtained to document optimal positioning. For needle placement, T2 axial and sagittal sequences were acquired summarized

in Table 2.


Utilizing Invivo prostate biopsy software, the lesion was

localized in the TZ far anteriorly at the mid gland level. The

DynaTRIM was calibrated and the needle track pathway was

then determined obtaining coordinates for the DynaTRIM.

Once the coordinates were obtained, the biopsy sleeve was

adjustedinthesagittal,axial,andcoronalplanes.Acoronal

obliqueconfirmationscanwasperformedtoconfirmadequate

needle track position through the lesion. Using the needle

graphicconfirmationdataset,an18-gaugecorebiopsyneedle

was advanced into the lesion and a core biopsy specimen

wasobtained.Aconfirmationscanbeforeremovalofthe

needle was performed to ensure optimal needle position.

The needle was removed and the core was placed in the

specimen container.

Figure 5 – OASIS with RAPID Body Coil and Invivo DynaTRIM patient setup. Body Flex coils for larger patients are available as used in this case.

Acquisition Plane TR (msec)

TE (msec)

Thick (mm)

FOV (cm)

Matrix Other Settings

Scan Time

FSE – T2Axial 6125 96 4.0 20 320x256 RADAR 1:42

Sagittal 5550 96 4.0 20 320x256 RADAR 2:56

Table 2 - Details of Our Prostate Cancer MR Guided Biopsy as Implemented on a 1.2T Scanner (Hitachi Medical Systems America)


MR Guided Biopsy Findings

Thepathologyreportconfirmedthetumorsuspiciousregion

is an adenocarcinoma of the prostate with a Gleason score

of 3+4=7. As a result of the scanning and diagnosis, the

Urologist referred the patient to a local cancer center to

undergo brachytherapy radiation therapy.

Discussion

Inthiscase,wehighlightedhowopenhigh-fieldMRI

platforms like the OASIS 1.2T can achieve good performance

characteristics for the effective detection and localization of

prostate cancer. Multiparametric Prostate MRI combined

with MRI targeted biopsy of any tumor suspicious region

substantiallyimprovesthedetectionofclinicallysignificant

prostate cancer with a high NPV and the overall accuracy

of the Gleason Scoring. The ability to conduct diagnostic

andinterventionalprostateMRwithouttheconfinement

or limitations of a closed-bore MR system will allow more

imagingoptionswithimprovedinterventionalworkflowfor

the Radiologist, and a more comfortable experience for

the patient.

Desert Medical Imaging (DMI) operates four imaging centers

in California located in Indian Wells, Indio, Palm Springs,

and Yucca Valley. All four of our facilities provide magnetic

resonance imaging (MRI), spiral computed tomography (CT)

imaging, and ultrasound. With vendor relationships that

allow DMI to partake in research and development of various

products, DMI has become a leader in prostate diagnosis and

treatment,performingthefirstFocalLaserAblationofprostate

cancer in an outpatient center in the world.

Dr. John F. FellerisaBoardCertifiedDiagnosticRadiologist

with a subspecialty in Orthopedic/Sports Medicine Imaging,

BodyMRI,andLevelIICardiacCTCertification.Dr.Feller

servedasanU.S.AirForceofficerandChiefofMRIatDavid

Grant USAF Medical Center and 15 years as an Assistant

Clinical Professor in the Department of Radiology at Stanford

University. Currently he is an Assistant Clinical Professor in

the Department of Radiology at Loma Linda University and

Founding Partner of DMI.

Figure 6 – (a) Axial T2WI (b) Sagittal T2WI sequences acquired for optimal needle positioning.

a b


Hitachi Medical Systems America, Inc.1959 Summit Commerce Park

Twinsburg, Ohio 44087 USA

Tel: 330.425.1313 800.800.3106

Fax: 330.425.1410

www.hitachimed.com

Hitachi Medical Corporation4-14-1 Akihabara UDX

Soto-Kanda, Chiyoda-ku

Tokyo, 101-0021 Japan

www.hitachi-medical.co.jp


0114/DM#95708v1

Printed in U.S.A.

Hitachireservestherighttochangespecificationsdescribed

herein without prior notice. This document provides general

technical descriptions of both optional and standard features.

case study | advanced apps on open deser… · standard for detecting prostate cancer, trus biopsy...

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