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The composition of atherosclerotic plaque in the carotid arteries is considered to be an important predictor of stroke risk. Specifically, plaques containing a large lipid core separated from the lumen by a thin fibrous cap are considered most vulnerable to rupture and subsequent embolus formation. Previous work has focused on characterizing the MR properties of various plaque components in excised specimens. The next step is to apply this knowledge to the development of an in-vivo imaging protocol for the monitoring of plaque progression/ composition in patients at risk for stroke. There are many challenges associated with in-vivo imaging of the carotid arteries, including decreased signal to noise ratio, patient movement, cardiac motion, and flow artifacts. To date, excellent progress has been made towards a comprehesive carotid imaging exam. We have optimized vessel wall imaging in patients using custom built rf coils, pulse sequence developments, and use of cardiac gating. These developments allowed us to obtain high quality images with 390 micron in plane resolution. Contrast-enhanced angiography was also performed in patients with a 0.8 mm isotropic resolution, with accurate depiction of vessel pathology. In conclusion, it is possible to obtain high quality images of carotid artery lumen and wall with MRI. This may provide a means to screen patients for surgery, or to monitor the effects of therapy on atherosclerotic lesion size.
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Figure 1: The contrast-enhanced
angiogram (a) illustrated a high grade
stenosis in the left internal carotid
artery of this patient. An axial black
blood image through the section of maximum
stenosis is shown in (b), and the arrow
indicates the atherosclerotic plaque,
which is shown in a magnified view in
(c). High resolution images of the excised
endarterectomy specimen (d) correlated
well with the in-vivo images.
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Figure 2: High resolution T2 weighted
MR image (a) correlates well with histology
with Movat's pentachrome stain (b). The
dark region indicated by the arrow is
a region of lipid and necrotic debris.
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1. The symptomatic carotid plaque,
Golledge, J et al., Stroke 2000;31:774-781
2. In vivo accuracy of multispectral magnetic resonance
imaging for identifying lipid-rich necrotic cores
and intraplaque hemorrhage in advanced human carotid
plaques. Yuan, C. et al. Circulation 2001;104:2051-2056.
3. Structure of Plaque at the carotid bifurcation:
high resolution MRI with histological correlation.
Coombs B. et al. Stroke. 2001;32:2516-2521.
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