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[Magnetic resonance angiography. Work in progress].

Rapid progress has been made in the development and clinical application of magnetic resonance (MR) techniques for creating angiogram-like images of blood vessels. Combinations of techniques such as gradient-echo pulse sequences and flow compensation (bright blood imaging) or presaturation (black blood imaging) permit the signal intensities of moving spins to be altered, so as to generate contrast between flowing blood and stationary tissues. Postprocessing of the images allows the creation of projection angiograms, which show the vasculature in a large slice of the body. Preliminary studies suggest a variety of potential clinical applications, including intracranial arteriovenous malformations and aneurysms, carotid artery disease, portal hypertension, renal artery stenosis, peripheral arterial disease and venous thrombosis. At present, MR angiography is not directly competitive with conventional contrast angiography because of lower spatial resolution and loss of signal from flow turbulence and from slow flow. Nonetheless, it is proving to be a useful clinical tool for the investigation of vascular pathology involving the head and body.