Dynamic subtraction contrast-enhanced MR angiography: Technique, clinical applications, and pitfalls

Rapid advances in techniques of contrast material-enhanced magnetic resonan ce (MR) angiography have enabled evaluation of the entire aorta and the mai n arteries. Dynamic subtraction MR angiography consists of first-pass imagi ng of long segments of arteries by using a three-dimensional fast field ech o sequence with multiple rapid bolus injections of a small dose of gadopent etate dimeglumine. Subtraction enables clear demonstration of the enhanced vascular lumen by eliminating background signal. Improved temporal resoluti on and repeated sequences after gadopentetate dimeglumine administration al low demonstration of arteries and veins separately. Double subtraction post processing can be used to eliminate arterial enhancement in demonstration o f the portal and systemic veins. Additional postprocessing can be used to d emonstrate arteries in a single image in patients with aortic dissection or a prolonged circulation time. To optimize the examination, the pulse seque nce, injection dose, injection rate, timing of the start of data acquisitio n, imaging time, breath holding, section thickness, and coil selection shou ld be considered. This technique is flexible enough to be applied in a vari ety of clinical settings, including atherosclerotic occlusive disease, aneu rysm of aortoiliac arteries, bypass graft, Takayasu arteritis, aortic disse ction, antiphospholipid antibody syndrome, renal artery disease, pelvic vas cular disease, and the portomesenteric venous system.