Enhancing the detector sensitivity of a Radio-Frequency surface resonator for Potassium-39 MRI at 18.7 MHz: Probing different geometries at various temperatures

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 maximize the detector sensitivity, its optimal size, geometry, and temperature was determined via Electro-Magnetic (EM) simulations and bench-top measurements. A two-turn spiral, circular, room-temperature surface resonator was then developed and applied for ³⁹K-MRI of a healthy live rat brain. Compared to the current-state-of-the-art as reported in the literature, the improved resonator sensitivity resulted in approximately five times higher SNR with twice faster acquisition time. As of the EM-simulations cryogenic-cooling could further improve the surface resonator´s sensitivity three-fold at 77 K (liquid nitrogen) and up to six-fold at 20 K (liquid helium).