Radio Frequency Sensing‐Based In Situ Temperature Measurements during Magnetic Resonance Imaging Interventional Procedures

Abstract Magnetic resonance imaging (MRI)‐tuned radio‐frequency (RF) sensors are used as a radiation‐free alternative for tracking minimally invasive medical tool positions. However, in situ temperature sensing capabilities of the MRI‐tuned RF sensors have not been thoroughly investigated yet. A self‐resonating RF sensor capable of remote in situ temperature sensing during real‐time interventional MRI is presented. The proposed RF sensor design relies on the temperature‐dependent permittivity to tune or detune the resonant frequency. The sensor is tuned to match the resonant frequency of a 7 Tesla MRI (298 MHz) at body temperature, enabling a hyperintense signal in MR images. As temperature increases, the sensor detunes due to the change in the relative permittivity, and the hyperintense signal disappears in the MR image, serving as a direct visual indicator of the temperature change in real‐time. In addition, the localized signal can be used for 3D position tracking of interventional medical devices. Using a 7 Tesla preclinical MRI, in vitro characterization and ex vivo feasibility of the proposed temperature sensing method are demonstrated in the clinically relevant temperature range of 36–42 °C with an accuracy of ±0.6 °C. Such RF sensors can provide safer operations in future MRI interventional procedures.