Evaluation of arterial bypass grafts of the pelvic and lower extremities with gadolinium-enhanced magnetic resonance angiography: comparison with digital subtraction angiography.

RATIONALE AND OBJECTIVES: The aim of this study was to compare contrast-enhanced magnetic resonance angiography (CE MRA) with digital subtraction angiography (DSA) in the assessment of patency and stenoses in bypass grafts. METHODS: Fifteen patients were examined with both CE MRA and DSA. Fifteen bypass grafts were evaluated by four readers for potential stenosis in five locations. The stenoses were classified in five types: 1 (0% to 24% stenosis), 2 (25% to 49%), 3 (50% to 74%), 4 (75% to 99%), and 5 (occlusion). RESULTS: Using both techniques, 70 of 75 evaluated locations (93.3%) were classified identically. This included six stenoses < 50% and six stenoses > 50%, respectively. Four of five overestimations of stenoses were scaled in DSA as stenoses type 1. One stenosis was categorized as type 3 in DSA. Sensitivity for CE MRA for detecting stenoses >or= 25% was 100% and the specificity 90%. Interobserver agreement for all evaluations was 0.77 (Spearman rank correlation test). CONCLUSION: In the assessment of low-grade stenosis in bypass grafts, CE MRA overestimates stenoses slightly but yields good results in comparison with DSA.