MRI-Guided Balloon Angioplasty to Treat Blood Flow Blockage in the Legs

Overview

This study will examine the use of magnetic resonance imaging (MRI) instead of x-rays to guide angioplasty in patients who require these treatments to treat blockages in leg arteries. Angioplasty is a procedure in which a balloon is inflated in a blocked artery to improve blood flow. MRI uses a magnetic field and radio waves rather than x-rays to show pictures of body tissues and organs. MRI shows all soft tissue, including the arteries, blood, and other organs, while the usual x-ray technique shows only the lumen of the artery when it is filled with dye, but not the vessel walls. Patients 18 years of age and older who require angioplasty with or without stenting to restore blood flow to the leg may be eligible for this study. Participants undergo the usual angioplasty procedure. The skin in the patient's groin area is numbed and a catheter is placed into the groin artery. The patient is given a blood-thinning medicine, and then other catheters are inserted to measure blood pressure and to inject a contrast dye to take pictures. Balloon catheters are inflated to open the blockage and, if needed, stents are put in place to maintain the opening. When the blood thinner wears off, the catheters are removed. Most of the procedure is conducted using MRI instead of X-rays to visualize the arteries and blockages. The patient is moved back and forth between the x-ray and MRI machines in a specially designed laboratory. If necessary, stenting, placement of a wire mesh to hold open the artery, is done using conventional x-ray techniques. The entire procedure, including MRI, takes up to 4 hours.

Cardiovascular interventional procedures are minimally-invasive, catheter-based treatments such as coronary artery angioplasty and stenting. These procedures generally can be conducted on awake patients with few complications, and were developed as alternatives to conventional open surgery. Conventional cardiovascular interventional procedures are conducted by physician manipulating medical devices inside patients under the guidance of fluoroscopic x-ray. We have developed minimally-invasive cardiovascular interventional procedures using real-time magnetic resonance imaging. These procedures have the advantage of excellent imaging without surgery and without ionizing radiation exposure or toxic contrast agents (dyes). Moreover, because real time MRI can produce excellent images of soft tissue, blood, and of three-dimensional structures, it may be possible to guide minimally-invasive procedures not possible even with invasive surgery. A state-of-the-art combined X-ray and MRI interventional suite has been constructed and equipped with real-time MRI image reconstruction for interventional experiments, patient monitoring and transport equipment for dual imaging modalities, and large-mammal preclinical simulation experiments. Preclinical experiments in a porcine model of surgical aortic coarctation have shown that real-time MRI guided percutaneous intervention can be conducted using entirely commercially-available devices approved by the US Food and Drug Administration. The goal of this protocol is to test clinical peripheral artery revascularization procedures guided wholly-or in part by real-time MRI.