Critical Lower-limb Ischemia: The Diagnostic Performance of Dual-phase Injection MR Angiography (Including High-resolution Distal Imaging) Compared with Digital Subtraction Angiography

Purpose To prospectively compare contrast-enhanced (CE) magnetic resonance (MR) angiography against digital subtraction angiography (DSA) in patients with critical lower-limb ischemia. Materials and Methods Thirty patients with critical lower limb ischemia underwent both CE MR angiography and DSA. CE MR angiography commenced with a dedicated high-resolution study of the below-knee arteries followed by a three-station bolus-chase examination. Two blinded observers recorded the severity of the most significant stenosis within each arterial segment. Interobserver agreement was calculated and, with DSA as the reference standard, the sensitivity and specificity of CE MR angiography for the detection of significant stenosis (≥50% luminal narrowing) or occlusion was calculated. Results All 390 arterial segments were scored by both observers. Sensitivity was higher in the distal segments (92%–96%) compared with the proximal segments (69%–79%). Specificity was similar in distal (90%–91%) and more proximal segments (86%–96%). Overall, interobserver agreement was excellent (κ = 0.95 for CE MR angiography and DSA) and was superior within the distal segments. Twenty-eight segments that were considered occluded on DSA were shown to be patent on CE MR angiography and 16 segments that were considered occluded on CE MR angiography were shown to be patent on DSA. Conclusions In patients with critical lower-limb ischemia, CE MR angiography with high-resolution distal imaging is highly accurate for assessment of the below-knee arteries. Both DSA and CE MR angiography may identify patent vessels that are considered occluded based on the other modality.