A phase contrast (PC) rephase/dephase sequence of magnetic resonance angiography (MRA): a new technique for imaging distal run-off in the pre-operative evaluation of peripheral vascular disease.

OBJECTIVE: To prospectively compare a 3-D phase contrast (PC) magnetic resonance angiography (MRA) sequence (rephase/dephase) with digital subtraction angiography (DSA) in pre-operative evaluation for femoropopliteal grafting in peripheral vascular disease. Assessment of distal run-off vessels and suggested siting of distal graft anastomosis to the above or below knee segment of the popliteal artery was made. METHODS: Twenty-two lower extremities booked for infra-inguinal vascular reconstruction were imaged pre-operatively using MRA and DSA. A PC rephase/dephase sequence which includes gradient motion refocusing (Siemens 1.0 T Magnetom Impact TR 50 ms, TE 14/14 ms and 15 degree flip angle) and 3-D MIP algorithm reconstruction was used to obtain the MR images. Standard techniques were used to obtain the DSA images, and the mean and median time between imaging modalities was one month. Blinded review by a consultant vascular radiologist scored nine vessel segments for each limb and assessed which popliteal arterial segment would be most suitable for distal anastomosis. RESULTS: The score from DSA and MRA agreed for 155/198 vessel segments (kappa 0.57) and the suggested siting for distal anastomosis agreed for 19/22 limbs (kappa 0.72). Eighteen limbs had surgery as planned (distal anastomosis to the above knee popliteal eight limbs, below knee popliteal 10 limbs). For three limbs the siting of the distal anastomosis suggested by DSA and MRA disagreed. The more accurate modality was proved for one of three limbs and showed MRA to be superior to DSA. CONCLUSION: Three-dimensional PC rephase/dephase MRA is a promising technique which compared well with DSA in the pre-operative assessment of distal run-off for femoropopliteal grafting.