Contrast-enhanced magnetic resonance angiography: Current status, theoretical limitations and future potential

Magnetic resonance angiography (MRA) is a method for visualizing blood vessels non-invasively. Although blood vessels are routinely demonstrated on all MR images, the term specifically refers to images where blood vessels are highlighted at the expense of background (i.e. non-vascular) tissues. The earliest form of MRA, black-blood angiography met with little enthusiasm for blood vessel imaging in clinical practice but remains in widespread use for cardiac imaging. MRA became a clinical reality with the introduction of gradient-echo imaging, a technique that depicted blood vessels as bright. However, it was only with the introduction of contrast-enhanced MRA (CE-MRA), a technique that generates images with high spatial resolution, inherent high vascular contrast and short scan times that MRA truly came of age and challenged, and in many cases supplanted, X-ray angiography as the technique of choice. This paper highlights the strengths and limitations of CE-MRA and addresses technological advancements in scanner performance and contrast agents that address the remaining clinical limitations of the technique.