Multi-layer RF coil design optimization for 23Na and 1H knee imaging at 7T

Motivation: Sodium MRI shows promise in detecting biochemical changes in cartilage and investigating meniscal root tears. Goal(s): To develop the RF technology needed to unleash the potential of 7T sodium imaging for knee applications. Approach: A multi-layer RF coil design was optimized through simulation exploring separate transmit-receive strategies, high density receive arrays, ultra-high permittivity material, and proton element integration strategies. Experimental testing validated multi-nuclear transmit performance. Results: An average SNR increase of ~40% and improved transmit performance was achieved for sodium by incorporating uHPM and a receive-only array. Proton imaging was possible without impacting sodium performance using flexible monopoles. Impact: The proposed multi-layer RF coil offers an SNR-optimized design for sodium imaging of the knee at 7T providing the resolution needed for robust biomarkers to diagnose and evaluate repair of damaged cartilage and meniscal root tears, primary causes of osteoarthritis.