MR angiography: present and future

Abstract

MR angiography is a rapidly evolving technique for noninvasive vascular imaging. Since 1985, when it was first shown to be clinically feasibls, the imaging techniques and hardware used for MR angiography have greatly improved. No longer is MR angiography a mere academic curiosity; it is already widely used to diagnose stenoses of carotid bifurcations and intracranial aneurysms. MR angiography supplements, and in some cases supplants, duplex sonography and CT for the study of suspected venous thrombosis in the chest, abdomen, and pelvis. With continuing technical developments, MR angiography most likely will replace conventional X-ray angiography in the presurgical workup of patients who are candidates for carotid endarterectomy or liver transplantation. Even MR angiography of the coronary arteries, considered implausible just a few years ago, has become feasible with the implementation of fast imaging techniques that suppress artifacts from respiratory and cardiac motion. Nonetheless, substantial problems remain that must be overcome before the full clinical potential of MR angiography can be realized. Despite the superficial similarities between MR angiograms and conventional angiograms, fundamentally different features of blood vessels are depicted. MR angiography is susceptible to a variety of artifacts that can exaggerate or simulate pathologic changes. The patient's cooperation is essential. The spatial resolution of MR angiography is inferior to its conventional counterpart, although the gap is being narrowed. This article reviews the basic principles of MR angiography and flow artifacts and surveys existing and future clinical applications.