Peripheral Vascular MRA

Editors-in-Chief: Eric A. Osborn, M.D., Ph.D. [mailto:eosborn@bidmc.harvard.edu] and Eli V. Gelfand, M.D. [mailto:egelfand@bidmc.harvard.edu] (Beth Israel Deaconess Medical Center, Harvard Medical School)

Introduction
Magnetic resonance angiography (MRA) is a non-invasive technique to image the lumen of blood vessels within the cardiovascular tree. While the gold standard remains intra-arterial contrast angiography, MRA has become a reliable tool with a diagnostic accuracy rivaling that of the invasive approach without the associated risks. It is increasingly being utilized for the diagnosis and pre-operative planning of vascular stenoses and other structural lesions.

Techniques

 * Spin echo (black blood sequences) are used to evaluate the vessel wall
 * 3D time-of-flight (bright blood sequences) are used for angiography
 * Phase contrast velocity mapping directly measures flow and is helpful in evaluating stenoses
 * Contrast enhancement (CE) with gadolinium improves the identification of blood and reduces artifacts
 * Novel contrast media for molecular imaging are being developed (see Molecular imaging and related novel technologies)

Carotid arteries
Fig. Carotid stenosis
 * Identification of:
 * Stenosis
 * Turbulent flow
 * Arterial thrombus

Aorta
Fig. Aortic dissection Fig. Abdominal aortic aneurysm
 * Identification of:
 * Aneurysms (complex, false, dissection flaps)
 * Flow velocity in true and false lumen
 * Involvement of branch arteries
 * Abscesses
 * Arch abnormalities
 * Coarctation
 * Supravalvular stenosis

Mesenteric arteries
Fig. Mesenteric stenosis
 * Anatomy: celiac, superior mesenteric, and inferior mesenteric arteries

Renal arteries
Fig. Renal artery stenosis

Peripheral arteries
Fig. Peripheral arterial lesion
 * Anatomy: iliac and infrainguinal arteries

Atherosclerotic plaque

 * Vessel wall imaging with MR plaque sequences characterizes the biological components of atherosclerotic lesions (lipid-rich/necrotic core, fibrous cap, hemorrhage, calcification, inflammation) and aides in the identification of ‘vulnerable’ plaques prone to rupture (see Atherosclerosis/Plaque Imaging with CMR).

Carotid stenosis

 * MRA vs. cerebral angiography - 2006 meta-analysis [reference]
 * Traditional TOF
 * 70-99% stenosis: sensitivity 88% and specificity 84%
 * 100% stenosis (complete occlusion): sensitivity 98% and specificity 100%
 * CE improves detection
 * 70-99% stenosis: sensitivity 94% and specificity 93%

Mesenteric stenosis

 * CE-MRA vs. angiography of the celiac and superior mesenteric arteries [reference]
 * Sensitivity 94% and specificity 100%

Renal artery stenosis

 * CE-MRA vs. angiography [reference]
 * Sensitivity 95% and specificity 92%

Peripheral arterial disease

 * CE-MRA vs. angiography [reference]
 * Sensitivity 93% and specificity 98%

Further online resources

 * Patient information about MRA from the American College of Radiology.