Disclosure Optimal Imaging Techniques for Research support is - - PowerPoint PPT Presentation

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Optimal Imaging Techniques for Surveillance of Aortic Dissection, Aortitis, and Related Syndromes

David Saloner, PhD

Department of Radiology and Biomedical Imaging VA/UCSF Medical Center San Francisco

Research support is provided by Siemens Medical Systems The use of Gadolinium and/or USPIO (Ferumoxytol) as contrast agents is an off-label use

Disclosure

Patients with vascular disease may present with similar conditions of the lumenal morphology. Some progress rapidly with devastating sequellae – others remain stable over many years. Can we determine the underlying pathology in the vessel wall and identify the markers of clinically relevant events?

Overview

Monitor lumen and wall over time Catheter angio – high lumenal resolution, dynamics invasive, no soft tissue, little flow US – reasonable resolution, non-invasive 2D, limited reproducibility CT – 3D, fast, lumen and wall, calcification poor soft contrast tissue, no flow, radiation MR – 3D, flow, non-invasive, excellent tissue contrast slow, motion sensitive

Modalities

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Monitor lumen and wall over time Catheter angio – high lumenal resolution, dynamics invasive, no soft tissue, little flow US – reasonable resolution, non-invasive 2D, limited reproducibility CT – 3D, fast, lumen and wall, calcification poor soft contrast tissue, no flow, radiation MR – 3D, flow, non-invasive, excellent tissue contrast slow, motion sensitive

Modalities CT Angiography

Excellent for rapid overview of aortic anatomy Single breathhold acquisitions Excellent lumenal depiction for identifying geometric morphology of lumen and wall Identify inflammatory responses in the wall In dissection, good visualization of intimal tear, intimal flap and reentry point

2 months later

Chest Pain

Convex towards false Systole Diastole

Aortic Dissection

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Aortic Dissection

Late Early

Aortic Dissection

CT Angiography

Iodinated contrast concerns Concern in surveillance for multiple radiation sessions Limited soft tissue information No flow information

Aorta Wall MR Imaging

MR offers many acquisitions with different contrast properties Excellent flow visualization No radiation 3D acquisitions with good reproducibility Potential for imaging inflammation

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Aortic Dissection - MRI

MRA CINE Black Blood

Aortic Disease

Post Contrast Fat Sat Black Blood

Aorta MR Imaging

AAAs are fusiform aneurysms that often present with large volumes of intralumenal thrombus Slab-selective 3D coronal acquisition For lumen: Bolus timing is key

CE-MRA 15 sec Gd Excellent lumenal visualization

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Aorta Wall MR Imaging

AAAs are fusiform aneurysms that often present with large volumes of intralumenal thrombus High contrast between wall and lumen using suppression

• f flow signal – black blood MR

Slab-selective 3D coronal acquisition – 1.3mm isotropic; Tacq = 7 minutes Large volumes of slow and recirculating flow present challenges for black blood MRI Breathing motion generates motion-related artifacts

Improved Contrast

DANTE SPACE

* * * *

All components of thrombus are isointense on CTA

A1 A2 A3 B1 B2 B3

Comparison with CT

CTA DANTE-SPACE

AAA Wall Imaging

3D SPACE provides images with 1.3mm**3 isotropic resolution Motion of abdominal organs can be problematic For serial comparison - lumenal segmentation is straightforward on MRA but outer-wall is difficult

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Molecular Imaging Research Ultrasmall Paramagnetic Iron Oxides (USPIO) in the wall as a marker of inflammation? Scavenged by activated macrophage Potentially differentiate stable from active (growing) aneurysms

Results

DANTE-SPACE

CE-MRA (USPIO)

Post Ferumoxytol D-SPACE

Multi-modality Imaging in a Rapidly Growing Iliac Artery Aneurysm

Comparison of USPIO (Ferumoxytol) with FDG-PET 3D – black blood vessel wall imaging

Ferumoxytol CT CT

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4D Flow Measurement Using MRI

Measure each component of velocity at all points in the 3D volume At any given point in time – connect the vectors to show streamlines Follow the vectors from one point in the cardiac cycle to the next to show path lines

4D Flow Streamlines 4D Flow pathlines

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4D Flow pathlines 4D Flow Measurement Using MRI

Flow patterns reflect the likelihood of thrombus layering Flow patterns reflect the presence of disordered or turbulent flow Flow patterns differentiate true and false lumen Velocity field – recirculation, jets, asymmetric flow, vortical flow Derived descriptors – wall shear stress, pressure drops, turbulence kinetic energy MR velocity methods require:

• a. Breathholding
• b. Administration of contrast agents
• c. Cardiac synchronization
• d. a and c
• e. b and c

MR velocity methods require:

• A. Breathholding
• B. Administration of

contrast agents

• C. Cardiac synchronization
• D. a and c
• E. b and c

B r e a t h h

• l

d i n g A d m i n i s t r a t i

• n
• f

c

• n

t r a . . C a r d i a c s y n c h r

• n

i z a t i

• n

a a n d c b a n d c

20% 20% 20% 20% 20%

:10

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MR velocity methods require:

• a. Breathholding
• b. Administration of contrast agents
• c. Cardiac synchronization
• d. a and c
• e. b and c

Compared to CT, advantages of MR are:

• a. Fast acquisition
• b. Improved soft tissue contrast
• c. Insensitivity to flow artifacts
• d. a and c
• e. b and c

Compared to CT, advantages of MR are:

• a. Fast acquisition
• b. Improved soft tissue contrast
• c. Insensitivity to flow artifacts
• d. a and c
• e. b and c

Imaging the Aorta

Multiple modalities available For surveillance: non-invasive reproducible structural and functional good contrast lumen and wall

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Radiology Siemens Medical Systems Chengcheng Zhu, PhD Gerhard Laub, PhD Henrik Haraldsson, PhD Sinyeob Ahn, PhD Farshid Faraji, MS Cecilia Huang, MS Florent Seguro, MD Michael Hope, MD Vascular surgery Chris Owens, MD Warren Gasper, MD Joseph Rapp, MD Hugh Alley

NIH (NINDS, NHLBI)