MR-guided balloon angioplasty: in vitro demonstration of the potential of MRI for guiding, monitoring, and evaluating endovascular interventions.

The purpose of this study was to demonstrate the potential of MRI for guiding, monitoring, and evaluating endovascular interventions. This was done by investigating the feasibility of MR-guided balloon angioplasty in a stenosed vessel model. Catheters and guidewires were prepared for susceptibility-based MR visualization by incorporating paramagnetic markers into their walls. Near real-time monitoring (up to 1 image/sec) of the interventional procedure was achieved by using a dynamic two-dimensional gradient-echo technique. Devices were localized by on-the-fly subtraction of a baseline image from consecutive dynamic images and by merging the subtraction images with a previously acquired road map. All steps involved in balloon angioplasty, from the introduction and placement of a guidewire to the positioning of a catheter across the stenosis, inflation of the balloon, and dilatation of the stenosis could adequately be monitored with MR fluoroscopy. The beneficial effect of dilatation could be substantiated by a reduction of stenosis-related hypointensities and hyperintensities in the posttreatment MR angiogram as compared to the pretreatment angiogram and by a posttreatment increase of the volumetric flow rate.

MR-guided endovascular interventions: susceptibility-based catheter and near-real-time imaging technique.

In a 47-year-old healthy male volunteer, susceptibility-based magnetic resonance (MR) imaging was performed in the basilic vein in the right upper arm at 1.5 T. A conventional 3-F nonbraided polyethylene catheter with a 0.3-mm lumen diameter was locally impregnated with dysprosium oxide, and six ringed areas of increased susceptibility were created. passive tracking of the catheter was performed with near-real-time conventional two-dimensional gradient-echo angiography. The entire prepared part of the catheter was depicted without steering problems or complications. Passive tracking is expected to provide a valuable adjunct to active tracking for guiding endovascular interventions.