Vascular Imaging in Stroke - CTA vs MRA
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Now that we've imaged the head,
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we're going to talk about imaging the vessels.
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CTA is the best way to image the vessels.
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It allows for most rapid evaluation of
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the vessels from the arch to the vertex.
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It allows you to determine hairline residual
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lumen versus occlusion, intravascular
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thrombus, and whether or not stents are
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reoccluded compared to MRA and ultrasound.
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And in the head, which we're going to get
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to a little bit later, it allows detection
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of large vessel occlusions with greater
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than 95% sensitivity and specificity.
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and allows rapid triage of
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patients for thrombolysis,
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and assessment of collateral circulation.
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So, these are some key carotid artery findings.
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You can see on the left here a patient with
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atheromatous disease and a critical stenosis.
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The vessel is so tight that
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the distal lumen is collapsed.
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On MRA, you might not even
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be able to see this, but this
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correlates nicely with a subsequent angio.
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So, critical stenosis with collapsed vessel.
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The next set of images is a
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patient with intraluminal thrombus.
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You can see on the sagittal, this filling defect
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and on the axial image, you can see
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this clot in the middle of the vessel,
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an MRA that can be confused with flow
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artifact and can be difficult to diagnose.
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That's intraluminal thrombus.
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And then, this is an example of a stent.
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You can see there's a stent here.
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And then on this MRA, you see signal dropout.
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You don't know if it's a critical stenosis.
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You really don't know what's going
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on there, but when you do a CTA,
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you can see that the vessel's patent.
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There's some narrowing from internal
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hyperplasia, but the stent's widely patent.
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So for critical stenosis, intraluminal
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thrombus and stents, CTA is really
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the best way to evaluate the vessels.
Pamela W Schaefer, MD, FACR
Professor of Radiology, Vice Chair of Education
Massachusetts General Hospital
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