Comparison of SAR distribution of hip and knee implantable devices in 1.5T conventional cylindrical-bore and 1.2T open-bore vertical MRI systems

Abstract

Purpose: There is increasing use of open-bore vertical MR systems that consist of two planar RF coils. A recent study showed that the RF-induced heating of a neuromodulation device was much lower in the open-bore system at the brain and the chest imaging landmarks. This study focused on the hip and knee implants and compared the specific absorption rate (SAR) distribution in human models in a 1.2T open-bore coil with that of a 1.5T conventional birdcage coil.

Methods: Computational modeling results were compared against the measurement values using a saline phantom. The differences in RF exposure were examined between a 1.2T open-bore coil and a 1.5T conventional birdcage coil using SAR in an anatomical human model.

Results: Modeling setups were validated. The body placed closed to the coil elements led to high SAR values in the birdcage system compared with the open-bore system.

Conclusion: Our computational modeling showed that the 1.2T planar system demonstrated a lower intensity of SAR distribution adjacent to hip and knee implants compared with the 1.5T conventional birdcage system.

Keywords: RF heating; RF safety; implant safety; open-bore MRI; orthopedic implant; vertical MRI.