Alterations in body and skin temperatures caused by magnetic resonance imaging: is the recommended exposure for radiofrequency radiation too conservative?

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Abstract
Increases in tissue temperature caused by exposure to radiofrequency (RF) radiation are a primary safety concern of magnetic resonance imaging (MRI). Therefore, body and skin temperatures were measured in six subjects before (20 min), during (30min) and after (20 min) MRI procedures performed at specific absorption rates (SARs) six to 10 times higher than the limit recommended by the UK National Radiological Protection Board. Body temperature was unchanged throughout the experiment. Abdominal skin temperature increased significantly (p<0.05) during MRI, decreased significantly post-MRI, but was still significantly (p<0.05) higher than baseline. The highest abdominal skin temperature recorded was 36°C. Upper arm, forearm and chest skin temperatures increased significantly (p<0.05) during MRI and remained elevated post-MRI. The highest skin temperatures recorded on the upper arm, forearm and chest were 38.1, 36.0 and 34.5°C, respectively. Thigh and calf skin temperatures were not significantly changed during MRI. These alterations in tissue temperatures were physiologically trivial and easily tolerated by the subjects, suggesting that the recommended exposure to RF radiation during MRI of the body for patients with normal thermoregulatory function may be too conservative.