MRI Retrospective Respiratory Gating and Cardiac Sensing by CW Doppler Radar: A Feasibility Study

Area of Science:

• Medical Imaging Physics
• Biomedical Engineering
• Electromagnetic Sensing

Background:

• Conventional MRI gating sensors can be challenging for specific patient groups.
• Non-contact sensing offers a potential solution to improve patient comfort and MRI workflow.

Purpose of the Study:

• To investigate the feasibility of non-contact respiratory gating and cardiac sensing using continuous wave (CW) Doppler radar within an MRI environment.
• To assess the compatibility and interference of radar sensing with MRI systems.
• To evaluate the potential of radar sensing for retrospective motion correction.

Main Methods:

• Utilized a software-defined radio operating at 2.4 GHz for CW Doppler radar.
• Demodulated in-vivo respiratory and cardiac signals.
• Validated radar functionality through electromagnetic simulations, bench tests, and human subject studies within the MRI bore.
• Compared radar sensing with electrocardiography, system bellows, and plethysmography.

Main Results:

• Demonstrated feasibility of non-contact cardiac rate sensing and dynamic breathing synchronization.
• Achieved in-bore motion correction for retrospective respiratory gating.
• Ensured MRI compatibility and interference-free operation through optimal radar design and spectral isolation.
• Observed minimal signal-to-noise ratio degradation (within 4.5%) on phantom images.

Conclusions:

• Confirmed the feasibility of in-bore retrospective motion correction using CW Doppler radar, independent of MRI system constraints.
• Non-contact radar sensing can complement existing MRI sensors and algorithms, potentially enhancing patient management and throughput.