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

Abstract

This work presents a galvanically coupled electron paramagnetic resonance spectrometer (GalEPR) for deep tissue oximetry and hypoxia diagnosis. Current in vivo EPR spectroscopy directly trades between the operation frequency (equivalent to sensitivity) and the penetration depth due to tissue absorption. Prior art is limited to 1.2 GHz/15 mm and 9 GHz/2 mm. To address this issue, a 30-MHz clock is galvanically coupled through the body to minimize attenuation and up-converted to 14 GHz by a low-power subsampling phase locked loop (SSPLL). The EPR spectrum is measured by an ultrasensitive low-power inductor sensor. The proposed GalEPR spectrometer demonstrates 14 GHz/50 mm frequency/depth (10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> better) with an in vitro hypoxia detection experiment.