Evaluating the accuracy of the variable flip angle technique for temperature measurement near metallic implants.

This study assessed the accuracy of a T1-based temperature measurement technique for metal-inserted materials using 3T magnetic resonance imaging (MRI). A variable flip angle (VFA) sequence with dual echoes was used to obtain images of a phantom and an experiment. T1 values were calculated when the metal-inserted materials were subjected to heating and were acquired in the proximity of the metal implant of the phantom and tissue. The values were converted into temperature measurements using a fiber-optic thermal sensor (FOS) that was placed within the metal substances. Additionally, proton resonance frequency shift (PRFS) was calculated from phase images acquired with the dual echoes, which allow for a comparison of temperature fidelity between the VFA and PRFS techniques. In the phantom experiment, the root mean square temperature error based on T1 values was approximately 0.12 ℃, which was comparable to that obtained from the FOS. In contrast, the PRFS demonstrated a substantial temperature measurement error of approximately 11.21 ℃, as determined by the root mean square calculation. A similar pattern was observed in the experiment, where the T1-based temperature measurement error was minimal at approximately 0.30 ℃, while the PRFS-based temperature measurement error was considerably higher at around 5.44 ℃. These findings indicate that the VFA technique enables precise monitoring of temperature alterations in metal-inserted materials, engendering its incorporation into clinical MRI sequences for temperature assessment during magnetic resonance radiofrequency (RF) exposure.