MR Angiography

Like CT Angiography, MRI also has the ability to perform non-invasive angiograms of many vessels in the body. Both CT and MR angiography rely on enhancement of the blood vessels of interest during rapid scanning of the region. Both of these techniques are referred to as "Non-invasive angoiograms" to distinguish them from traditional invasive angiograms, which require an arterial catheter to be placed (usually via the groin), and direct arterial injection of iodinated contrast. Both MR and CT angiography can be interchangeably used in most instances. The most common reason to choose an MR over a CT angiogram is a personal history of renal function abnormality or history of allergic reaction which makes CT not an option.

MR angiography can take advantage of two different techniques and contrast enhancement methods to produce MR angiograms: IV contrast enhanced MR angiography. This requires an IV injection of MR Contrast Material. As this circulates through the heart and then out into the arterial system of the body, rapid MR scanning is timed to coincide with the arrival of the contrast in the body. 3D reformations are then performed to achieve an MR Angiogram.

"Time of flight" MR Angiography relies on flow related enhancement of arteries to achieve contrast. This does not require an IV contrast injection, but relies on an MR phenomenon of flow related enhancement to produce bright vessels. This technique is routinely only used in the evaluation of the cerebral arteries.

Common applications of MR Angiography are similar to those for CT Angiography and are as follows:

• Renal arteries (in hypertensive patients)

• Carotid arteries

• Aorta (evaluation for aneurysms)

• Cerebral arteries (frequently looking for a cerebral aneurysm)

• Legs (in patients with symptoms relating to atherosclerotic narrowing in the arteries of the legs)