corevalve ® msct scan acquisition and processing march 2013 innovating for life. uc201305577 ee

CoreValve® MSCT Scan Acquisition and Processing

March 2013

Innovating for life.UC201305577 EE

AcademiaMedical Education

INTERNATIONAL. CAUTION: For distribution only in markets where CoreValve® is approved. Not for distribution in U.S. or Japan. Medtronic, Inc. 2013. All Rights Reserved.

The MSCT Sizing Process

The sizing process includes three main parts, all of equal importance:

– Proper image acquisition and post-processing– Reformatting of the aortic root and preparation for

measurement– Aortic root measurements and device selection

(covered earlier in presentation)



MSCT Scan Acquisition



Multi-detector CT scanner (64-slice minimum) with ECG-gating capability.

– The scans of the aortic root MUST be ECG-gated.Non-gated scans in areas with cardiac motion lead to measurement inaccuracy and therefore incomplete information for device selection.

– Peripheral vessel image acquisition may be non-gated.

Post-processing software capable of MPR and standard measurements (diameter, area, perimeter)

– This is typically standard on most imaging system workstations

– This is also available on many second party applications

Equipment Required



1. Chest topogram2. ECG-gated contrast enhanced aortic root3. Non ECG-gated contrast enhanced peripheral

vessels

Sub-millimeter slice thickness is required for scans 2 and 3

Scans Required



• The scan protocol is similar to a CT coronary angiogram.

• The aim is to get adequate contrast in the region of interest (i.e., endo-luminal surface) for visualization of left heart, aorta, and peripheral access vessels (i.e., femorals and subclavians) when necessary.

• Temporal resolution should be optimized to reduce motion artifact.

• Spatial resolution should be as high as possible (goal is smallest isotropic voxel size for high-quality MPR).

Scanning Procedures



• Administer medication per institution standard practice for CT scanning.

• Attach ECG electrodes for gating of scan. Verify quality of ECG tracing on scanner console.

• Prepare large intravenous line (18 or 20 gauge) for administration of contrast media.

• Instruct patient to lie still during scan, even if they experience warmth or tingling due to the injection of contrast.

• Instruct patient in practice of breath-hold at end-inspiration for 10-15 seconds (duration required will depend on specific scanner performance). Assess heart rate variability during breath-hold. If heart rate is >65 bpm or unstable, consider titration of beta-blockers.

Step 1: Patient Preparation



Acquire a chest topogram for use in planning the imaging protocol.

Step 2: Topogram



• Intent: Assessment of aortic root and valve anatomy

• Coverage area – Suggested: Superior to aortic arch - inferior to cardiac

apex– Minimum: 10 mm below aortic annulus – 70 mm above

aortic annulus (includes the aortic root and direct aortic access)

• Retrospective or prospective ECG-gating may be usedReconstruct or trigger in systole

• Required detector collimation of 0.4 – 0.625 mm• Required slice thickness of < 1 mm• Recommended slice overlap of 0.4 mm

Step 3: Contrast Enhanced Scan Parameters



Minimum Coverage

Area

Recommended Coverage Area



• Prepare iodinated contrast injection apparatus.• Set up scan parameters per the table on slide 17. • Instruct patient to lie still during scan, even if they experience

warmth or tingling due to the injection of contrast. • Initiate contrast injection. • When contrast reaches threshold at bolus-tracking location,

instruct patient to hold breath at end-inspiration, then initiate main scan protocol.

• At completion of scan verify images are of adequate quality.• Record amount of contrast given. • Record heart rate average and range.

Step 3: ECG-Gated, Contrast Enhanced Scan Execution



• Verify heart rate ECG triggers are at consistent place in cardiac cycle, edit if necessary. Additional editing/removal of arrhythmias may be performed.

• If retrospective gating is used: – Reconstruct the cleanest systolic phase from a signal-noise ratio and motion

artifact perspective. – Automated “best-systolic” reconstruction can also be used.– < 1 mm slice thickness with small overlap

Step 4: Post-processing of Aortic Root Images



ECG-Gated, Contrast Enhanced Scan Parameters Recommended Parameters

IV injection with iodine contrast

80-100 (320mg/ml or higher), modify per patient as appropriate

Injection rate 4-6 mL/sec

Bolus tracking, delay Delay time calculated using protocol for current scanner (bolus tracking or similar) with peak of contrast concentration in the ascending aorta during acquisition.

ECG Leads Required

ECG-gating Prospective or Retrospective

Scan direction Cranial-caudal

Scan coverage From above the aortic arch to past the cardiac apex

Detector collimation 0.4 – 0.625 mm

Pitch 0.2–0.43 adapted to the heart rate

Dose modulation If retrospective, modulation and full current between 30 and 80% of the cardiac cycle

Slice thickness 0.8 mm

Slice overlap 0.4 mm

Reconstruction kernel Medium Smooth

Post-processing Reconstruct the cleanest systolic phase from a signal-noise ratio and motion artifact perspective.

Automated “best-systolic” reconstruction can also be used.

Reconstructed slice thickness <1 mm.



• Intent: Assessment of peripheral access vessels• Standard radiology CT angiography protocol• Non ECG-gated• Delay time calculated using protocol for current scanner (i.e.,

bolus tracking) with peak of contrast concentration in the area of interest

• Suggested coverage areas: – Femoral access only screening: abdominal aorta above celiac artery

and down to the femoral head– Subclavian access only screening: above the subclavian arteries and

down to mid-thorax– Combined access screening: above the subclavian arteries and down

to the femoral head• Source data reconstructed using < 1 mm slice thickness with

small overlap

Step 5: Non-gated, Contrast-Enhanced Scan of the Peripheral Access Vessels



MSCT Scan Processing



• The aortic annulus is not co-planar with the planes of the body (i.e., axial, sagittal, or coronal).

• Therefore, multi-planar reformatting of the CT images is required to create a double-oblique axial image for annulus measurements.

• This reformatting is critical; if the plane is not correctly aligned, it may be passing through the sinuses or the LVOT. This can lead to improper device selection.

• This reformatting is also used in assessing the measurements for the rest of the aortic root (sinus width, height and ascending aorta diameters).

• The following methods are similar to those reported in Schultz et al. EuroIntervention Supplement (2010) Volume 6 (Supplement G) G6-G13.

Proper Aortic Annulus Measurements



Example images in original orientation (axial, coronal and sagittal). Red curved arrow and line indicate adjustment of coronal and sagittal planes to align with aortic annular plane.

Step 1: Multiplanar Reformat

AxialCoronal

Sagittal 3D



Step 2: Verify Aortic Annular Plane

Example images of reformatted oblique coronal (upper left), oblique sagittal (lower left), double oblique (upper right) and 3D reconstruction (lower right). Yellow triangles indicate most basal attachment points of the aortic valve.

Double Oblique

AxialOblique Coronal

Oblique Sagittal 3D



The Aortic Annulus on MSCT

Descending Aorta

Aortic Annulus

RVOT

RA

LA

LAA



Example of Incorrect Plane – Too Low

Example images of reformatted oblique coronal (upper left), oblique sagittal (lower left), double oblique (upper right) and 3D reconstruction (lower right). The double oblique axial image is located approximately 10 mm into the LVOT.

Double Oblique


Oblique Sagittal 3D



Example of Incorrect Plane – Too High

Oblique Coronal

Double Oblique

Axial

ObliqueSagittal

Example images of reformatted oblique coronal (upper left), oblique sagittal (lower left), double oblique (upper right) and 3D reconstruction lower right. The double oblique axial image is located a few mm into the aortic root and the leaflets are

visible.

Double Oblique


Oblique Sagittal 3D



Example of Incorrect Plane – Wrong Orientation

Example images of reformatted oblique coronal (upper left), oblique sagittal (lower left), double oblique (upper right) and 3D reconstruction lower right. The double oblique axial image is located in the wrong orientation as the right

coronary leaflet is visible while the others are not.

Double Oblique


Oblique Sagittal 3D



CoreValve® is a registered trademark of Medtronic CV Luxembourg S.a.r.l. For more information and a complete list of adverse events, warning and contraindications reference CoreValve IFU.

corevalve ® msct scan acquisition and processing march 2013 innovating for life. uc201305577 ee

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