SHAPE Society

1. MR Imaging for the Evaluation of
Carotid Atherosclerosis
David Saloner, PhD
Professor of Radiology
VA Medical Center
University of California San Francisco

2. What is the risk factor associated
with carotid disease?
a b c d
Identical diameter stenosis but different geometries
and/or composition

3. Standard of truth - excised specimen

4. High Resolution MRI of Resected Plaque
• Provides perspective on wealth of
information available from MR imaging of
geometry and composition
• (200µm)3
resolution (not currently obtainable
in vivo)

5. Longitudinal MRI
Transverse MRI
Carotid specimen

6. 0
10
20
30
40
50
60
circular crescentic elliptic lobular
frequency
Cross-section through
maximal stenosis for
9 specimens
Stenosis shape

7. Fibrous cap over necrotic core
Histology MRI
MRI shows good contrast between fibrous cap and
necrotic core as confirmed on histology

8. High Resolution MRI In Vivo
• Can we obtain comparable data in vivo that will
provide measures of 3d descriptors?
Will these permit us to follow the progression of
geometry (X-sectional area, plaque bulk), and
compositional features (lipidic core, fibrous cap)?
• Can we identify the features of the plaque that
correlate with rapid progression in a prospective
fashion?
• Can we identify the features of the plaque that confer
neurological risk?

9. High resolution
TOF-MRA using
high sensitivity
phase-array carotid
coil
0.7mm x 0.7mm x1.0mm
Tacq = 6min

10. time
carotid jugular
Inject 30cc
Ttr
Td
Acquisition time
Intravenous injection
of GdDTPA -
contrast enhanced
MRA (CE-MRA)
-can be used to
address some
shortcomings of
conventional MRA.

11. CE-MRA 3D TOF
CE-MRA (25 s) has
little motion blurring
compared to 3D
TOF (10 min)

12. CE-MRA 3D TOF
CE-MRA
(TE=1.5 ms)
has reduced
sensitivity to
complex flow cf
3D TOF
(TE=6.5ms)

13. CE-MRA
3D TOF
Caveat: CE-MRA not always better.
Tight stenosis seen as flow void on
CE-MRA

14. Dedicated
equipment provides
improvements -
phased-array carotid
coil gives increased
SNR hence better
resolution
Conventional coil Phased-array coil

15. High-resolution 3D imaging of lumenal contours

16. High resoln. MRA of lumenal contours in vivo
• Provides good delineation of vascular contours
with reasonable resolution - about 0.5 mm3
voxel
• 3D depiction of contours
• Little or no invasiveness
• Provides potential to evaluate cross-sectional area,
and surface irregularities

17. Native image
with coil
Adjusted image
Phased-array coils with postprocessing

18. Calcification
Calcification also noted on MRI

19. High resoln. MRI of vessel wall in vivo
• Provides good delineation of plaque components
with reasonable resolution - about 0.5 mm3
voxel
• Sequential 2D slices providing 3D overview
• Non invasive
• Provides potential to evaluate plaque
inhomogeneity - perhaps lipid core, fibrous cap,
calcification, intraplaque hemorrhage

20. Dr. David Saloner, VASF, and Dr. F. Scott Pereles, Northwestern
High Resolution
Carotid Imaging
3D CE-MRA 3D TrueFISP 2D T2-TSE
New rapid methods - new hardware

21. Future of MRA/I
• Improved hardware and software
• Use of 3D black blood studies, plaque enhancement
following contrast injection
• Implementation in longitudinal studies of disease
progression/regression
• Establish true determinants of neurological risk