Acoustic noise levels generated during high field MR imaging.

Although much has been published highlighting the safety risks of magnetic resonance imaging, little mention has been made of acoustic noise levels. As the clinically available gradient strengths of MR systems increase, acoustic noise levels will become more important. Measurements were made of the acoustic noise levels generated by magnetic resonance imaging on two high field systems (1.0T and 1.5T). These data were compared with those in the literature. On the 1.0T magnetic resonance system, comparisons were also made between data acquired using the standard gradient system (maximum levels of 10m T/m) and a new upgraded gradient system (maximum levels of 15m T/m). The results show that many sequences produce noise levels above the safe levels defined by the Department of Health and the Health and Safety Executive. Providing routine ear protection for patients is, therefore, important. Noise levels for the upgraded gradient system on the 1.0T scanner are in the range of 2 dB greater. As expected, noise levels generated were greater for the 1.5T magnetic resonance imager than on the 1.0T system.