An Optimized Room-Temperature RF-Surface Resonator for in vivo Potassium-39 MRI at 9.4 T - Simulation and Measurement Study for Cryogenic Coils

Ibrahim A. Elabyad¹, Raffi Kalayciyan¹, Nagesh Shanbhag², Lothar Schilling², Lothar R. Schad¹

Potassium-39 (39K) Magnetic Resonance Imaging (MRI) is a non-invasive technique which could potentially allow for detecting intracellular physiological variations in common human pathologies such as stroke and cancer. However, the low signal-to-noise ratio (SNR) achieved in 39K-MR images hampered data acquisition with sufficiently-high spatial and temporal resolution in animal models so far. In order to improve the detector SNR gain, its optimal size, geometry, and temperature were determined via electromagnetic (EM) simulations and bench-top measurements. An optimized single-loop room-temperature surface resonator was then developed and tested for 39K-MRI of a healthy live rat brain. Compared to the previous published results of a triple resonant coil (1H, 23Na, and 39K), the developed resonator improve the SNR eight times with twice faster acquisition time. As experienced in the EM-simulations cryogenic-cooling of the optimal single-loop coil could further improve the SNR gain three-fold at 77 K and up to six-fold at 20 K. These significant results could further improve the available signal in future 39K-MR imaging studies of the rat brain at 9.4 T.