MRI with MR Angiography in Endovascular Repair of Abdominal Aortic Aneurysms

Abstract: The aim of this study was to evaluate MRI with contrast enhanced MR angiography (MRI/CE MRA) as imaging method before and after endovascular repair of abdominal aortic aneurysms (AAA). A 1.5 T scanner was used for all examinations. In this prospective study 26 consecutive patients were included. Follow-up was performed between February 1995 and May 2002 (median follow-up; 36 months, range 8-84 months). In Paper I, we assessed the value of MRI/CE MRA as follow-up method. MRI/CE MRA provided the relevant information. MRI was the sole method demonstrating intramural thrombus organization and vertebral body infarction. In Paper II, we evaluated MR safety; ferromagnetism and heating of a nitinol stent-graft. Image artefacts were also evaluated on MRI/CE MRA and CT. In addition, an extended MR protocol including velocity mapping was assessed. MRI in a 1.5 T system may be performed safely in patients with the nitinol stent-graft (Vanguard). MRI/CE MRA provided diagnostic image information with only minor metal artefacts. Image evaluation on CT can be disturbed at the graft limb junction and graft bifurcation by the beam hardening artefacts. MR velocity mapping did not provide additional information. In Paper III, we compared measurements for stent-graft planning. MRI/CE MRA was compared with DSA and CT. The MRA post processing techniques MIP and VRT were also compared. The length measurements obtained with MRA-MIP were significantly shorter, but probably more correct, than those obtained with DSA. The diameter measurements obtained with MRI/CE MRA were more variable. Improvements of the MRA technique and a standardized determination of the vessel boundaries are needed for more reliable diameter measurements. In Paper IV, we compared costs of follow-up with MRI/CE MRA with costs of follow-up with CT with DSA, or CTA. The cost analysis included a risk analysis of contrast media induced nephropathy. MRI/CE MRA can be cost-effective for follow-up depending on the risk of contrast media induced nephropathy for CT with DSA, or CTA. In Paper V, we presented mid-term results with the Stentor and Vanguard stent-grafts assessed with MRI/CE MRA. Complications and secondary interventions were common. Long-term follow-up is mandatory. This study has shown that for MR-compatible stent-grafts, MRI/CE MRA could be the method of choice for follow-up of endovascularly repaired AAA. For patients with pre-existing renal insufficiency MRI/CE MRA should be the method of choice.