Contrast agents in magnetic resonance imaging.

With the advent of magnetic resonance imaging (MRI) it has become apparent that paramagnetic contrast agents may have a place in clinical practice. The mechanism of action, development, techniques of use and initial animal and clinical results are reviewed. Gadolinium diethylene triamine penta acetic acid (Gd3+-DTPA) has proved an effective paramagnetic contrast agent in experimental animals and clinical trials with this agent commenced in November-December 1983. Gd3+-DTPA will cross a damaged blood-brain barrier, is excreted mainly by glomerular filtration and is distributed mainly in the extracellular space. No short-term toxicity has been detected. Long-term toxicity is, as yet, unknown. Optimum dose, pulse sequences and timing of imaging remain to be determined by further studies but Gd3+-DTPA shows promise as a useful addition to MRI.