Study uncovers no adverse effects from exposure to 9.4T

Safety concerns that restrict the use of MR scanners to field strengths below 8T may not be warranted, based on research results presented May 24 in Berlin.

Volunteers exposed to a 9.4T static magnetic field at the University of Illinois experienced no statistically significant change in vital sign measurements or cognitive ability. They reported only mild discomfort, such as a spinning sensation, when being moved through the magnetic field.

Human experiments above 8T currently require approval by the FDA and the investigational review board of individual institutions. The Illinois research found no evidence, however, of significant risk at such fields.

The research team, which included staff from the University of Illinois Center for MR Research and psychiatry department, as well as GE Healthcare's Applied Science Laboratory, compared results from volunteers exposed to a custom-built 9.4T MR scanner with an 80-cm bore to those obtained when the 10 subjects, four female and six male between the ages of 20 and 63, were exposed to a mock MR scanner with no magnetic field.

Neuropsychological testing assessed working memory, information processing speed,

memory and learning, and level of fatigue. Vital signs, obtained using an MR-compatible patient monitoring system, captured heart rate, blood pressure, O₂ saturation, and skin temperature during the actual and mock MR scans.

When in the 9.4T field, sodium imaging was performed for up to 60 minutes using a custom-built modified birdcage RF coil. An audio recording simulating the noises encountered during such an exam was played when volunteers were in the mock scanner.

Anxiety, lightheadedness, and sleepiness were reported during both the real and mock exams. Metallic taste, a spinning sensation during table movement, and muscle twitching or tingling were reported only by subjects in the magnet.

Neuropsychological tests uncovered no statistically significant differences in performance under either condition. The researchers reported no significant changes in vital signs due to the mock or actual scans.