Impact of Patient Body Posture on RF-Induced Energy Absorption by Orthopedic Plates

Abstract

This study investigates variations in radiofrequency- (RF-) induced energy absorption by orthopedic plates within the human body during 1.5T and 3T magnetic resonance imaging (MRI) scans, considering diverse postures. Using the poseable Duke model, we developed typical postures (O-posture, X-posture, Y-posture, and Z-posture) and placed anatomically correct representations of various orthopedic plates within these postures. Numerical simulations were conducted to evaluate electromagnetic fields and RF-induced energy absorption in these postures near orthopedic plates during MRI scans. Comparing RF-induced energy absorption (peak spatial averaged SAR over 1 g, pSAR_1g) in postured models to the original posture reveals substantial variations. The pSAR_1g differences for X-posture, Y-posture, and Z-posture reach 48%, 134%, and 32% at 1.5T, and 36%, 83%, and 101% at 3T, respectively. Changing posture can lead to higher or lower pSAR_1g. These findings underscore the impact of patient posture on RF-induced energy absorption in orthopedic plates on the ulna bone. The study recommends considering representative body postures in future evaluations for MR conditional labeling of passive implants. Until then, maintaining a neutral posture during MR scans is advised to mitigate unforeseen RF-induced heating risks.