Magnetic Resonance Angiography

Magnetic resonance angiography (MRA) has excited the interest of many physicians working in cardiovascular disease because of its ability to noninvasively visualize vascular disease. Its potential to replace conventional x-ray angiography (CA) that uses iodinated contrast has been recognized for many years, and this interest has been stimulated by the current emphasis on cost containment, outpatient evaluation, and minimally invasive diagnosis and therapy. In addition, recent advances in magnetic resonance (MR) technology resulting from fast gradients and use of contrast agents have allowed MRA to make substantial advances in many arterial beds of clinical interest. The goal of this scientific statement is to present the current state of MRA of the extracranial arteries and to suggest current as well as possible future clinical applications for MRA. For the purposes of this statement, MRA is defined as MR techniques that provide cross-sectional or projectional images of normal and diseased arterial anatomy. It does not deal with the equally important area of quantitative flow measurement with MR. The first section deals with the technical basis of MRA. Subsequent sections deal with individual vascular beds in which MRA has shown clinical promise. The “gold standard” for many manifestations of vascular disease, especially arterial occlusive disease, is CA, an invasive, costly, and potentially hazardous procedure. MRA could represent an alternative, noninvasive approach. Rather than a single technique, MRA actually represents a family of different techniques. As outlined below, contrast between blood and soft tissues is derived from completely different MR mechanisms in the various MR techniques. We will consider the basic principles underlying the MR imaging (MRI) appearance of flowing blood and the techniques used to image blood flow and render angiogram-like MRI scans. Depending on the imaging technique used, blood may appear bright or dark. On traditional spin-echo MR images, blood vessels usually …