Endovascular procedures under near-real-time magnetic resonance imaging guidance:: An experimental feasibility study

Purpose: The purpose of this study was to assess the feasibility of insertion of endovascular stents and the precision of an open-field interventional nlagnetic resonance imaging (iMRI) system in an in vivo model, Methods: A feasibility study was undertaken at a university-affiliated hospital. Three male piglets with an average age of 6 months and a weight between 70 and 77 kg and two 3-month-old male piglets that weighed 40 to 44 kg were anesthetized. The five piglets underwent placement of nitinol stents inserted through the right femoral artery under the guidance of a SIGNA-SP 0.5T open-configuration iMRI unit. With a dedicated high-resolution near-real-time MRI sequence, the stent was guided and deployed onto a predefined target. Results: The main outcome measures were the duration of the procedure from the beginning of positioning to the end of deployment of the stent, the final position of the stent in relation to the target on the iMRI screen, and comparison with autopsy findings. Three stents were deployed within the aorta at the level of the renal arteries, and two were deployed within the right iliac artery just below the aortic trifurcation, The average duration of the endovascular deployment was 13 minutes. There was an agreement of 0.6 mm in the position of the stent as observed on iMR images and found at autopsy. When the piglets were sacrificed, the average distance between the stents and the predefined target was 7.8 mm, mostly because of the migration of one stent. Axial views allowed for accurate determination of stent impaction on the vascular wall. Conclusions: This study confirms the feasibility of stent deployment under near-real-time MRI guidance. It also emphasizes some inherent characteristics that hold promise with regard to other conventional techniques: stents and vascular structures are visualized in near-real-time in any desired plane, and the technique is performed without the potential adverse effects of ionizing radiations and iodinated contrast agents.