[Contrast-enhanced three-dimensional angiography].
Rapid advances in the techniques of contrast-enhanced MR angiography (MRA) have made it possible to evaluate the entire aorta and main arteries as well as small arteries and veins of the whole body. In this article, the technical aspects and clinical applications of contrast-enhanced MRA are reviewed. Dynamic contrast-enhanced three-dimensional (3D) MRA is a first-pass vascular imaging technique that uses the 3D fast field echo sequence with rapid bolus injection of contrast material. By repeating imaging sequences, it is possible to trace the dynamics of the injected contrast material over time and apply various postprocessing techniques, such as double subtraction and addition, to demonstrate arteries and veins separately and to display the arteries in a single image, even when circulation time is prolonged. This technique is flexible enough to be applied in a variety of clinical settings by optimizing the examination. The abdominal aorta and main arteries of the lower extremities are examined by two methods, dynamic subtraction 3D MRA (MRDSA) and the moving-bed method. Three bolus injections of contrast material are used in MRDSA. In contrast, a slow continuous injection of a large dose (20 ml or more) of contrast material is used in the moving-bed method, which is a convenient, useful method of contrast-enhanced MR angiography when the study must focus on arterial imaging. Clinical indications include atherosclerotic occlusive disease, Takayasu arteritis, aortic dissection, anti-phospholipid antibody syndrome, aneurysm, patent and occluded bypass graft, and deep vein thrombosis, among others. The problem with contrast-enhanced MRA is its difficulty in depicting small vessels such as mesenteric arteries, distal renal arteries, and peripheral small arteries. The nature of gradient-echo sequences has certain inherent problems for the imaging of small vessels. The fat-tissue interface becomes dark because of chemical shift artifact (which occurs both when the echo time is set in-phase and when it is set out-of-phase), reducing the ability to detect small arteries with contrast-enhanced MR angiography. The fat suppression technique is very useful for satisfactorily demonstrating small vessels by reducing chemical shift artifact. MR angiography remains an exciting and challenging field, and the best methods of contrast-enhanced MR angiography will be developed and established on the foundation of all previous work.
Watanabe
Y
Y
Department of Radiology, Kurashiki Central Hospital.
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media / Q000008:administration & dosage; D006801:Humans; D021621:Imaging, Three-Dimensional; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged
D003287:Contrast Media