Objective: This study investigates the feasibility of non-contact retrospective respiratory gating and cardiac sensing using continuous wave Doppler radar deployed in an MRI system. The proposed technique can complement existing sensors which are difficult to apply for certain patient populations. Methods: We leverage a software-defined radio for continuous wave radar at 2.4 GHz to detect in-vivo respiratory and cardiac timescrolled signals. In-bore radar signal demodulation is verified with full electromagnetic simulations, and its functionality is validated on a test bench and within the MR bore with four normal subjects. Radar sensing was compared against well-known references: electrocardiography on a test bench, system bellows, and pulsed plethysmography sensors with in the MRI bore. Results: The feasibility of noncontact cardiac rate sensing, dynamic breathing sequence synchronization, and in-bore motion correction for retrospective respiratory gating applications was demonstrated. Optimal radar front-end system arrangement, along with spectral isolation and narrow bandwidth of operation, enable MRI-compatible and interference-free motion sensing. The signal-to-noise-ratio degradation by the radar integration was within 4.5% on phantom images. Conclusion: We confirmed that in-bore retrospective motion correction using CW Doppler radar is feasible without MRI system constraints. Significance : Non-contact motion correction sensing in MRI may provide better patient handling and through put by complementing existing system sensors and motion correction algorithms

This study investigates the feasibility of non-contact retrospective respiratory gating and cardiac sensing using continuous wave Doppler radar deployed in an MRI system.

HighlightsAbsence of dedicated MRI coils often limits diagnostic imaging performance, especially in small field of view applications. Our goal was to achieve high resolution Temporomandibular joint MRI at 3T using local floating resonat ing coil inserts combined with a commercial head array. We design, im plement, and evaluate a size-optimised wireless dual-turn loop resonator on a pad and its arrangements within a 48-channel commercial head coil using loaded and unloaded cylindrical phantoms. In vivo volunteer images validate the proposed design for high-resolution imaging in a small field of view. Local small loop resonators and their arrangement within a conventional head coil result in significant SNR gain in the region of interest without compromising parallel imaging performance for both phantom and in vivo images. The size optimized, easy-to-handle local wireless resonators, and their arrangement within a conventional head array significantly improve Temporomandibular joint imaging performance, allowing diagnostic benefits at 3T in the absence of a dedicated coil.