Exposure to electromagnetic fields in the magnetic resonance imaging environment in South Africa

Abstract

Occupational exposure to radiofrequency (RF) and static magnetic fields at magnetic resonance imaging (MRI) suites is of continuing concern to personnel who routinely work in this environment. Questions regarding the levels of occupational RF and static field exposure have increased with the increasing demand for anesthetics to be administered in this environment. The present study was thus designed towards addressing the above-mentioned problem by gaining information regarding exposure levels of clinical personnel at MRI units in South Africa. Three 1.5 MRI units in Bloemfontein, South Africa were utilized to evaluate the exposure of clinical personnel to the electromagnetic fields present in the MRI environment over a period of time and during different clinical MRI procedures. Three rounds of measurements of RF fields in the MRI environment were done. All the three measurement rounds were focused on the low frequencies, 5 Hz–32 kHz, as well as on the high frequencies, 300 kHz–40 GHz. First round measurements were done to establish the background of the RF fields in and around the magnet room during an MRI examination. Second round RF field measurements were done at a specific location, 1 m away from the bore on the right-hand side of the bed, in the MRI room. The third round measurements were of the same format as the second round, but the specific location was against the magnet bore. Two pieces of Narda Safety Test Solution instruments, the EFA-300 and EMR-300, were used to measure the electromagnetic and magnetic exposure fields generated from the MRI scanners. Results of the measurements indicate that the electromagnetic fields measured during different clinical procedures do not exceed the International Commission on Non-Ionizing Radiation Protection (2000) guidelines in these units. Results from round two and three showed that the RF and gradient exposure 1 m and up against the bore entrance does not exceed these guidelines (rms average over 6 min). Ongoing new developments in MRI scanning create the need for continuously monitoring exposure of patients and workers to the EMF fields in the MRI environment.