Time-resolved contrast-enhanced MR angiography of renal artery stenosis: Diagnostic accuracy and interobserver variability

OBJECTIVE. The purpose of this study was to evaluate diagnostic accuracy an d interobserver variability of time-resolved three-dimensional gadolinium-e nhanced MR angiography in the detection of renal artery stenosis in compari son with intraarterial digital subtraction angiography as the standard of r eference. SUBJECTS AND METHODS. Forty consecutive patients (age range, 25-81 years; m ean. 62.9 +/- 11.9 years) with suspected renal artery stenosis underwent in traarterial digital subtraction angiography and gadolinium-enhanced MR angi ography, performed on a 1.5-T system with fast low-angle shot three-dimensi onal imaging (3.8/1.49 [TRITE], 25 degrees flip angle, 10-sec acquisition t ime, and 1.5-mm partition thickness). Three time-resolved phases were obtai ned in a single breath-hold. Digital subtraction angiography and gadolinium -enhanced MR angiography were evaluated by four observers who studied 80 ma in renal arteries and 19 accessory vessels to evaluate the degree of stenos is. A stenosis reducing the intraarterial diameter by more than 50% was reg arded as hemodynamically significant. Interobserver variability was calcula ted. RESULTS. Only one gadolinium-enhanced MR angiography study was not of diagn ostic quality, as a result of failure of the power injector. All main branc hes were of diagnostic quality in 38 (97.4%) of the remaining 39 gadolinium -enhanced MR angiography studies. Seventeen (89.5%) of 19 accessory renal a rteries were depicted with gadolinium-enhanced MR angiography. The overall sensitivity for significant stenoses was 92.9%. The overall specificity was 83.4%, and the overall accuracy was 85.9%. Interobserver variability of ga dolinium-enhanced MR angiography exceeded that of digital subtraction angio graphy. CONCLUSION. Time-resolved three-dimensional gadolinium-enhanced MR angiogra phy is a useful noninvasive method of screening suspected renal artery sten osis because of its easy application, short examination time, and high sens itivity despite of its higher interobserver variability.