A Galvanically Coupled Electron Paramagnetic Resonance Spectrometer for Deep Tissue Hypoxia Diagnosis

An electron paramagnetic resonance (EPR) spectrometer for deep-tissue oximetry and hypoxia diagnosis is presented. The existing in vivo EPR spectrometers suffer from a direct tradeoff between the operating frequency (equivalent to sensitivity) and the sensing depth due to human body EM absorption, and only achieve 1.2GHz/15mm or 9GHz/2mm. To break the tradeoff, this work galvanically couples a 30MHz source through the tissue and multiplies it up with a SSPLL to reduce EM absorption. It achieves 14GHz EPR frequency and 50mm sensing depth. In vitro hypoxia detection is demonstrated with this approach.