MRI RF-Induced Heating in Heterogeneous Human Body with Implantable Medical Device

Abstract

Magnetic resonance imaging (MRI) radio frequency (RF)-induced heating is one of the most important concerns of MRI safety for patients, especially with orthopaedic healthcare products. In this chapter, numerical modelling and simulations were conducted to study the RF-induced heating within a 1.5T and 3T magnetic resonance (MR) environment. Numerical simulations were firstly conducted to study the difference between the cases of implantable medical devices inside the phantom and the human body. Then, numerical modelling were conducted to describe the difference of electromagnetic behaviours between the homogeneous phantom and heterogeneous human tissues. The MRI RF-induced heating due to an implantable medical device behaves significantly different in homogeneous media and in heterogeneous human body. For typical orthopaedic medical devices, such as healthcare products applied to shoulder, humerus, hip, femur and tibia, the properties of the RF-induced heating are different in general phantom and in human body. The hot spot location, as well as worst case configuration were evaluated and it was found that they were determined by the incident field and electromagnetic properties of medium. With further scaling, the RF-induced heating in human body for the orthopedic devices can be assessed by phantom studies.

Body‐loop related MRI radiofrequency‐induced heating hazards: Observations, characterizations, and recommendations

“…To quantitively and experimentally study the RF‐induced heating caused by the trunk‐arm loop posture, based on the postures from Figure 1G, and to validate the simulation results, a customized phantom is developed as shown in Figure 2A. The customized phantom is designed based on the standard ASTM phantom 35,36 mimicking a human body trunk. The dimensions of the customized phantom are shown in Figure 2B.…”

Computational Investigation of the Factors That Affect Tangential Electric Fields along Cardiac Lead Paths inside MRI Birdcage Coils

“…Therefore, because of the high degree of complexity during the interaction between the MRI coil and the implant, the results of previous works measured in homogenous phantoms might not provide enough confidence regarding patients' safety as the patient's body composition alters the RF power deposition in the tissue surrounding implanted leads [18][19][20][21][22][23]. In [24], the RF-induced electric field inside a homogenous phantom was assessed, demonstrating a different spatial distribution compared to the respective distribution inside a human model [25].…”

Electromagnetic simulation of RF burn injuries occurring at skin-skin and skin-bore wall contact points in an MRI scanner with a birdcage coil

“…Because the relationship between the SAR and temperature distribution is not straightforward [17], temperature simulations have also been performed [15,18,19] to meet the IEC standard for normal operating mode; this standard states that the body core temperature should not increase by more than 0.5 ℃. These types of computer simulation methods have been widely used for RF heating analysis [20][21][22][23][24], especially for cases involving implants [21][22][23]25,26], as they can be used to ensure MRI compatibility in terms of RF heating of medical implantable devices [27]. The computer simulations provide a convenient way to evaluate the local SAR and the aforementioned temperature increase; however, there are no computer-simulation-based studies that have focused on the most frequent RF burn injuries, which occur at skin-skin and skin-bore wall contact points.…”