Review of radiofrequency heating and burn injuries caused by magnetic resonance imaging

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This review describes the current progress in understanding radiofrequency (RF) heating effect and injuries, particularly burns, that have occurred in patients during magnetic resonance imaging (MRI) procedures. MRI scans are produced by applying a strong static magnetic field, a fast-varying magnetic field gradient, and a RF field. While MRI injuries remain rare, the frequency of accidents is increasing in parallel to the increasing application of high magnetic field strength. RF burn injuries constitute nearly half of all MRI related injuries and are increasing. RF burn injuries occur either due to skin to skin contact or skin contact with a wire/cable or a wire acting as an antenna that interacts with the RF field of the MRI machine. Considerable local heating occurs that is concentrated at the contact points of the wire or skin, however, the mechanism for some of the RF burn injuries occurring at contact points is not well understood. This poses challenges for the application of adequate safety or preventive measures for RF related burns in MRI procedures.

Progress in Understanding Radiofrequency Heating and Burn Injuries for Safer MR Imaging

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The review provides state-of-the-art knowledge on RF heating and burn injuries in medical MRI systems, including RF exposure limits. Internationally, the RF exposure limits for MRI procedures are guided by the recommendations of the International Commission on Non-Ionizing Radiation Protection (ICNIRP). These RF exposure limits are given in terms of specific absorption rate (SAR in W/kg), which is essentially the amount of RF energy absorbed per unit mass of human tissue. SAR limits applicable for the use of passive implants (e.g., hip and knee prostheses) or active implantable medical devices (e.g., cardiac pacemakers or cochlear implants) have been documented in other standards such as ASTM-F2182 and ISO/TS 109474:2018, respectively. 

The review also recommends key preventive measures to avoid the likelihood of RF related burns in MRI procedures. The recommendations include the use of foam pads (1-2 cm thick) to insulate the patient from cables, the bore, and between limbs to prevent RF burn injuries, avoiding positioning the body near the RF transmit coil and considering the antenna effect for patients with large implants and tattoos. These recommendations are consistent with those provided by the Royal Australian and New Zealand College of Radiologists (RANZCR).

In conclusion, this review is a useful guide to understanding MRI related RF burn injuries in medical imaging settings.