3T ³¹P/¹H calf muscle coil for ¹H and ³¹P MRI/MRS integrated with NIRS data acquisition

Purpose: Our aim was to design and build a 3T ³¹P/¹H calf coil that is capable of providing both good ³¹P and ¹H transmit and receive performance, as well as being capable of accommodating a near-infrared spectroscopy (NIRS) device for simultaneous NIRS data and MRI/MRS acquisition. Method: In this work, we propose a new 3T ³¹P/¹H birdcage combination design consisting of two co-centrically positioned birdcages on the same surface to maximize transmit efficiency and sensitivity for both nuclei. The ³¹P birdcage is a high-pass birdcage, whereas the ¹H birdcage is a low-pass one to minimize coupling. The diameter of the ³¹P/¹H birdcage combination was designed to be large enough to accommodate a NIRS device for simultaneous NIRS data and MRI/MRS acquisition. Results: The one-layer coil structure of the birdcage combination significantly streamlines the mechanical design and coil assembly process. Full-wave simulation results show that the ³¹P and ¹H are very well decoupled with each other, and the ¹H and ³¹P SNR surpasses that of their standalone counterparts in the central area. Experiment results show that the inclusion of a NIRS device does not significantly affect the performance of the coil, thus enabling simultaneous NIRS and MRI readouts during exercise. Conclusion: Our findings demonstrate the feasibility and effectiveness of this dual-tuned coil design for combined NIRS and MRS measurements, offering potential benefits for studying metabolic and functional changes in the skeletal muscle in vivo.