Emerging nuclear magnetic resonance technologies. Health and safety

NMR imaging (MRI) and spectroscopy have been applied to an increasing number of patients and volunteers for 10 years. The field strength has increased by a factor of 10 since 1979 and the switched gradients have increased by over a factor of 10 since 1980. RF absorbed power has increased by almost a factor of 10 in many studies due to both the increase in frequency and the increase in duty cycle associated with new RF pulse protocols. Even with these increases, all available evidence argues that the clinical procedures offer no hazards to human subjects. Known hazards associated with flying ferromagnetic objects, internal prostheses, and wires or metal objects in contact with the skin of patients can be avoided. Although hazards are not expected for the present procedures, emerging methods using fast scan strategies and higher frequency RF of the higher fields will require a closer vigilance and will demand continuing experimental and theoretical work such as detailed in this symposium.