Flexible Segmented Surface Coil Resonator for In Vivo EPR Measurements in Human Subjects

• Published in: Applied magnetic resonance Vol. 53; no. 1; pp. 145 - 165
• Main Authors: Petryakov, Sergey, Schreiber, Wilson, Kmiec, Maciej, Swartz, Harold M., Schaner, Philip E., Kuppusamy, Periannan, Williams, Benjamin B.
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01.01.2022; Springer Nature B.V
• Subjects: Atoms and Molecules in Strong Fields; Cables; Continuous radiation; Design optimization; Diameters; Harold M. Swartz: On the Occasion of His 85th Birthday; Human motion; Human subjects; Laser Matter Interaction; Magnetic fields; Optimization; Organic Chemistry; Original Paper; Oximetry; Oxygen; Physical Chemistry; Physics; Physics and Astronomy; Physiology; Resonators; Segments; Sensitivity; Sensors; Signal averaging; Solid State Physics; Spectroscopy/Spectrometry; Weight reduction
• ISSN: 0937-9347; 1613-7507
• DOI: 10.1007/s00723-021-01408-0

There is a strong need to enable accurate and convenient oxygen measurements in vivo for human subjects to improve treatments for cancer, peripheral vascular disease, and other diseases where tissue oxygen levels have a significant impact. While EPR spectroscopy has the potential to do this effectively, the full exploitation of these capabilities requires optimization of resonators for use with human subjects. Patient motion, and its effects on resonator coupling and positioning relative to the implanted oximetry probe, is a major source of noise and artifacts. Additionally, optimization of detection sensitivity to enable measurements from tissues at depths of several centimeters with clinically practical acquisition times is needed. To meet these needs, surface resonators with high sensitivity and flexible cables that allow the detection loop to be conveniently attached to the skin surface were developed for use with low frequency (L-Band, 1.15 GHz) continuous wave EPR. These resonators include a multi-segment sensing loop with a common capacitance. The light-weight segmented sensing loops, with diameters of 10–20 mm, can be connected to a commercial topical fixation applicator to conveniently and securely position them on patients’ skin surfaces. It was shown that a resonator of 20 mm in diameter makes it possible to obtain adequate EPR signals in tissue phantoms up to a depth of 20 mm with ~ 2 min of signal averaging. This novel lightweight resonator design, with sensitive multi-segment design and flexible cable with skin surface attachment, significantly reduced the impacts of subject motion enabling reliable EPR oximetry measurements in human subjects.