A Comprehensive In-Silico Study on MRI Safety of Pedicle Screw Systems Using Bone-Inclusive Phantom

This paper introduces a bone-inclusive phantom designed to improve the accuracy of radiofrequency (RF) energy absorption assessments for pedicle screw systems under 1.5T MRI conditions. A total of 225 numerical simulations were performed to evaluate electromagnetic fields and RF-induced energy absorption, encompassing three distinct modeling strategies: a conventional device-only phantom, a bone-inclusive phantom, and a human body model. The results in this study demonstrate that for small screws the device-only phantom simulations align more closely with the human body model while bone-inclusive phantom simulations achieve higher accuracy as screw size increases. Notably, for longer pedicle screws, the bone-inclusive phantom more accurately identifies the location of the peak specific absorption rate (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{pSAR}_{1 \mathrm{g}}$</tex>) at the rod tip, whereas the device-only phantom erroneously indicates the screw tip as the site of maximum absorption. These findings show the importance of incorporating critical skeletal structures and carefully selecting device and bone dimensions when conducting phantom-based simulations for implantable devices, as these factors significantly enhance the fidelity and accuracy of the resulting RF energy absorption predictions.