Peripheral Vascular MRA

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Editors-in-Chief: Eric A. Osborn, M.D., Ph.D. [1] and Eli V. Gelfand, M.D. [2] (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)

Clinical applications

Carotid arteries

• Identification of:
  • Stenosis
  • Turbulent flow
  • Arterial thrombus

Fig. Carotid stenosis

Aorta

• Identification of:
  • Aneurysms (complex, false, dissection flaps)
    • Flow velocity in true and false lumen
    • Involvement of branch arteries
  • Abscesses
  • Arch abnormalities
  • Coarctation
  • Supravalvular stenosis

Fig. Aortic dissection Fig. Abdominal aortic aneurysm

Mesenteric arteries

• Anatomy: celiac, superior mesenteric, and inferior mesenteric arteries

Fig. Mesenteric stenosis

Renal arteries

Fig. Renal artery stenosis

Peripheral arteries

• Anatomy: iliac and infrainguinal arteries

Fig. Peripheral arterial lesion

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).

Validation

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.

References

1. ref1 PMID 15523304