Comparison of Magnetic Resonance Angiography and Standard Angiography in Diagnosing Atherosclerosis

Overview

This study will evaluate ways to improve magnetic resonance angiography (MRA) for diagnosing atherosclerosis (hardening and narrowing of the arteries). MRA is a new method for looking at arteries and veins without standard angiography, which requires inserting a catheter into a blood vessel, injecting a contrast material, and obtaining X-ray images. Current MRA techniques, however, do not depict the lumen (cavity) of small vessels well enough to accurately determine the extent of their narrowing. This study will test image processing methods with the eventual goal of improving MRA accuracy to the point that it can replace X-ray catheter angiography for diagnosing atherosclerotic disease. Patients with atherosclerosis who have had conventional angiography at Suburban Hospital in Bethesda, MD, may be considered for this study. They will be screened with a brief history and physical examination, and those enrolled will have a MRA scan within 72 hours of their conventional angiogram. For this procedure, a catheter is placed in a vein in the patient's arm and the patient lies on a table that slides into a magnetic resonance imaging (MRI) scanner-a large donut-shaped machine with a magnetic field. Surface coils-flexible, padded antennae used to improve the quality of the pictures-are wrapped around the patient's legs. At times during the scan, the patient is asked to hold his or her breath for several seconds, and a contrast material called gadolinium is injected through the catheter in the vein. This substance enhances the images of blood flow in the vessels. The procedure generally takes about an hour and a half, although the actual imaging takes only a small part of that time.

Contrast Enhanced Magnetic Resonance Angiography (MRA) is a developing technology for the non-invasive evaluation of arterial and venous structures which does not require x-ray based catheter angiography. While dramatic progress in MRA has recently been made, there are still substantial limitations in the accuracy of MRA in grading stenoses and detecting small accessory vessels. The purpose of this study is to recruit patients with documented atherosclerotic disease as confirmed on catheter angiography performed at Suburban Hospital for evaluation with state-of-the-art MRA on MRI units, also at Suburban Hospital. We intend to test new surface coils, new pulse sequence designs, and advanced image processing algorithms in order to improve MRA accuracy to the point that a large-scale study of MRA vs. conventional angiography is possible. The goal of this pilot study is to improve MRA to the point that it can reliably replace diagnostic x-ray catheter angiography in the evaluation of patients with atherosclerotic disease.