Final diagnosis
Aortic aneurysm, renal artery stenosis.
Differential diagnosis
None.
Discussion
The evaluation of the abdominal aorta and all its branches, including distal arteries of the lower limbs has been highly improved by using high gradients, 3D fast gradient echo acquisition (3D EF-GRE) after injection of a bolus of Gadolinium. We currently use this protocol on a 1.5 T GE Echospeed (Milwaukee) for the evaluation of patients presenting with multiple locations of atherosclerosis.
Using a Field of View of 42 cm, four levels are consecutively acquired by moving the table by 30 cm steps, in order to cover vessels from the diaphragm down to the feet. Total acquisition time is approximately 1min 30 s.
Using a pump, a mean volume of 40 cc of Gadolinium is injected with a bolus technique, at the rate of 0.5 cc/s, followed by fast infusion of saline. Acquisition is started when enhancement is detected within the upper aorta.
Ingestion of ferrite is a effective adjunct to prevent from artifacts induced by intestinal fluid.
Suppression of the signal from fat associated with the 3D EF-GRE allows to easily generate high-contrast 3D-MIP reconstruction of the vasculature, with a minimum post processing time. Multiple views are especially useful in evaluating renal and mesenteric arteries, iliac and femoral bifurcations, as well as stenotic arteries and aneurysms.
In addition, slightly delayed acquisitions show some enhancement within the aortic wall, allowing a better delineation of thrombus within the aneurysm, not well evaluated by angiography.
MR angiography limitations include a low flow detection and spatial resolution within distal vessels in some patients compared to selective angiography, and early opacification of commitant veins which sometimes cannot be easily differentiated from arteries.