Numerical calculation of temperature increase during MRI due to the presence of total hip replacement implants

Abstract

Introduction Patients carrying active or passive implants are often excluded from MRI scanning, because of the potential tissue heating, due to the RF radiation emitted by volume or surface coils. Several studies have tried to quantify the resulting temperature rise and, consequently, assess implant compatibility. Purpose The purpose of the current study is to demonstrate the feasibility of evaluating with numerical modeling the worst-case temperature rise in tissues undergoing MRI scanning, due to total hip replacement implants. Materials and methods The simulated setup includes two different CAD models of a total hip replacement implant embedded in the ASTM F2182 phantom filled with tissue mimicking gel. The phantom is placed inside a birdcage RF coil resonant at 64 MHz (1.5T). The SEMCAD-X package is used to solve numerically with the FDTD technique the coupled electromagnetic and heat-transfer problems, in order to calculate the temperature rise in the gel. The results are obtained for a continuous exposure of 20 min to 2 W/kg whole-body SAR, which is the limit for normal operating mode. Results The results show that the maximum energy deposition appears at the tip of the implant stem. The temperature rise in the gel at this point can reach 12 °C, depending on the materials of the implant. There is also a local maximum in the temperature rise next to the implant head, but its value is half or less than that at the tip. Conclusion It is possible to successfully apply modern computational techniques in the timely assessment of medical implants compatibility, thus shortening their development process and increasing patient safety. Disclosure Authors declare that they have no competing interests.