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In this study, our purpose was to compare the high-resolution contrast-material-enhanced three-dimensional subtraction MR angiography with conventional angiography for occlusive disease in the pelvic and lower extremity arteries. A three-dimensional fast-imaging with steady precession (FISP) sequence with a 256 x 512 matrix was obtained on 1.5T MR unit using a phased array coil. Twenty patients with arteriosclerotic obstructive disease underwent subtraction dynamic contrast-enhanced MR angiography. In 15 patients, three regions (pelvis, upper knee, and lower knee) were sequentially obtained after repeated injection of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA). In the other five patients, one region was imaged (total of 50 examinations); a maximum-intensity projection (MIP) algorithm was used for subtracted images. All patients also underwent conventional angiography. Angiographic images were divided into several anatomical segments. Three blinded radiologists independently graded a total of 50 anatomic segments with stenotic or obstructive diseases and 90 segments without disease. Subtracted images allowed resolution of small branch vessels in all examinations, although misregistration was seen in eight examinations of five patients. All arteries larger than 1 mm in diameter were visualized on subtracted images. For detection of significant stenosis (>50%), MR angiography had 96% sensitivity and 83% specificity. The correlation coefficient of degree of agreement between MR angiography and conventional angiography was .92. Stenotic vessels tended to be overestimated. We conclude that high-resolution dynamic contrast-enhanced three-dimensional MR angiography is capable of depicting small vessel anatomy of the pelvis and lower extremities. Sequential MR angiography of different regions was feasible by repeated injection of Gd-DTPA and subtraction. This technique is highly sensitive in detecting lesions, but stenosis tended to be overestimated.
Yamashita et al. (Tue,) studied this question.