Magnetic field strength issues in magnetic resonance imaging.

The authors review the current status of magnetic resonance imaging (MRI) with respect to magnetic field strength. The discussion covers the practical aspects of MRI--safety, throughput and costs--as well as the clinical aspects as they are influenced by field strength. Data on the world distribution of MRI units of various field strengths are presented. Canada had the highest proportion of high-field units among the 11 countries or regions included in this comparison, probably because most Canadian MRI units are located in teaching hospitals, where they are used for both research and clinical work.