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

Abstract

RF electromagnetic wave exposure during MRI scans induces heat and occasionally causes burn injuries to patients. Among all the types of physical injuries that have occurred during MRI examinations, RF burn injuries are the most common ones. The number of RF burn injuries increases as the static magnetic field of MRI systems increases because higher RFs lead to higher heating. The commonly believed mechanisms of RF burn injuries are the formation of a conductive loop by the patient's posture or cables, such as an electrocardiogram lead; however, the mechanisms of RF burn injuries that occur at the contact points, such as the bore wall and the elbow, remain unclear. A comprehensive understanding of RF heating is needed to address effective countermeasures against all RF burn injuries for safe MRI examinations. In this review, we summarize the occurrence of RF burn injury cases by categorizing RF burn injuries reported worldwide in recent decades. Safety standards and regulations governing RF heating that occurs during MRI examinations are presented, along with their theoretical and physiological backgrounds. The experimental assessment techniques for RF heating are then reviewed, and the development of numerical simulation techniques is explained. In addition, a comprehensive theoretical interpretation of RF burn injuries is presented. By including the results of recent experimental and numerical simulation studies on RF heating, this review describes the progress achieved in understanding RF heating from the standpoint of MRI burn injury prevention.

Case report: Radiofrequency-induced thermal burn injury in a dog after magnetic resonance imaging

“…Theoretical heating of the tissues of the patient caused by the RF pulses is evaluated by the SAR, which is depicted in watts per kilogram bodyweight. The SAR can be calculated taking into account the patients height, weight, and the scan settings such as for example RF pulse frequency and the angulation of the RF magnetic field ( 18 ). There are guidelines with upper allowable SAR values for safe MRI examinations in humans.…”

“…Two bottles of warm water wrapped in a blanket were placed next to the patient's abdomen and the patient was covered with a blanket. The following sequences were included for the study the brain: dorsal T1 weighted (W) inversion recovery (TR 2.4s, TE 18 MRI showed severe extradural spinal cord compression at the level of the C3-C4 intervertebral disc, lateralized to the left side of the spinal canal (Figure 3). A hydrated nucleus pulposus extrusion was diagnosed.…”

Unveiling the Temporal Aspect of MRI Tattoo Reactions: A Prospective Evaluation of a Newly-Acquired Tattoo with Multiple MRI Scans

“…Currently, darker shades appear to be more prone to MRI reactions. Conductive materials, particularly those in elongated shapes such as sensor leads, are more susceptible to radio frequency (RF)-induced thermal heating during MRI scans, known as the “antenna effect.” It has been hypothesized that spiral tattoos can form conductive loops, thereby increasing the risk of thermal reactions, but the current literature does not offer evidence to support this hypothesis [ 8 ]. Since the available reports are derived from individual scans, the temporal aspect of the problem has been insufficiently represented in the data to warrant a study [ 1 ].…”