Toroid-inspired RF Volume Coils for Enhanced Transmit Efficiency at Ultra-Low Field 47mT MRI: A Comparison with Solenoid Coils

Motivation: Ultra-low field MRI is often limited by low SNR, challenging its viability for clinical use. Novel RF coil designs could improve these aspects, enabling better image quality and diagnostic potential. Goal(s): To assess whether a toroid-inspired RF coil can improve B1+ field efficiency and homogeneity more than widely used solenoids at ultra-low field MRI. Approach: We used electromagnetic simulations to compare the transmit efficiency of single and multiple-wound toroid coil designs to an elliptical solenoid coil operating at 47mT. Results: The quadruple-wound toroid volume coil outperformed the solenoid in both B1+ efficiency and field homogeneity in simulations. Impact: This work suggests that toroid-inspired RF coils may offer a more efficient and homogeneous transmit field at ultra-low field MRI, supporting the development of affordable, high-quality imaging systems.