Thresholds for perceiving metallic taste at high magnetic field

PURPOSE: To perform an initial characterization of the metallic taste effect observed by some workers when moving around an MRI scanner. MATERIALS AND METHODS: A total of 21 subjects performed controlled movements in the stray field of a 7-T scanner. Rates of change of magnetic flux were recorded during the study using a custom-built three-axis coil unit connected to a data logger. RESULTS: Relatively normal movements could generate switched fields of 2 T/second. Of the 21 subjects, 12 detected a metallic taste, but the threshold at which it was perceived varied greatly between subjects, with the minimum dB/dt value at which such a taste was detected being 1.3 T/second. The threshold also depended on the direction of movement. CONCLUSION: This study indicates that 50% of subjects will perceive a metallic taste for head shaking with a period of 1.5 seconds (magnetic field in an anterior/posterior direction) causing a dB/dt of 2.3 +/- 0.3 T/second. The presence of dental fillings is not a requirement for the sensation of metallic taste.