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 inserti on 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 hosp ital. Three male piglets with an average age of 6 months and a weight betwe en 70 and 77 kg and two 3-month-old male piglets that weighed 40 to 44 kg w ere anesthetized. The five piglets underwent placement of nitinol stents in serted 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 tar get. 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 fin al position of the stent in relation to the target on the iMRI screen, and comparison with autopsy findings. Three stents were deployed within the aor ta at the level of the renal arteries, and two were deployed within the rig ht 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 auto psy. When the piglets were sacrificed, the average distance between the ste nts and the predefined target was 7.8 mm, mostly because of the migration o f one stent. Axial views allowed for accurate determination of stent impact ion on the vascular wall. Conclusions: This study confirms the feasibility of stent deployment under near-real-time MRI guidance. It also emphasizes some inherent characteristi cs that hold promise with regard to other conventional techniques: stents a nd vascular structures are visualized in near-real-time in any desired plan e, and the technique is performed without the potential adverse effects of ionizing radiations and iodinated contrast agents.