Hand‐held electron spin resonance scanner for subcutaneous oximetry using OxyChip

• Published in: Magnetic resonance in medicine Vol. 92; no. 1; pp. 430 - 439
• Main Authors: Almog, Nir, Zgadzai, Oleg, Kuppusamy, Periannan, Zur, Yehonatan, Baruch, Limor, Machluf, Marcelle, Blank, Aharon
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.07.2024
• Subjects: Artificial tissues; compact magnet; Electron paramagnetic resonance; Electron spin; Electron spin resonance; Electron Spin Resonance Spectroscopy; Equipment Design; Humans; Magnetic fields; Magnets; Oximetry; Oximetry - methods; OxyChip; Oxygen; Partial pressure; Phantoms, Imaging; pulsed ESR; Scanners; Skin; Skin - diagnostic imaging; Skin grafts; Spin resonance; Therapeutic applications; tissue pO2; Wound healing; pulsed ESR; oximetry; tissue pO2; OxyChip; compact magnet
• ISSN: 0740-3194; 1522-2594; 1522-2594
• DOI: 10.1002/mrm.30066

Purpose Electron spin resonance (ESR) is used to measure oxygen partial pressure (pO2) in biological media with many clinical applications. Traditional clinical ESR involves large magnets that encompass the subject of measurement. However, certain applications might benefit from a scanner operating within local static magnetic fields. Our group recently developed such a compact scanner for transcutaneous (surface) pO2 measurements of skin tissue. Here we extend this capability to subsurface (subcutaneous) pO2 measurements and verify it using an artificial tissue emulating (ATE) phantom. Methods We introduce a new scanner, tailored for subcutaneous measurements up to 2 mm beneath the skin's surface. This scanner captures pulsed ESR signals from embedded approximate 1‐mm oxygen‐sensing solid paramagnetic implant, OxyChip. The scanner features a static magnetic field source, producing a uniform region outside its surface, and a compact microwave resonator, for exciting and receiving ESR signals. Results ESR readings derived from an OxyChip, positioned approximately 1.5 mm from the scanner's surface, embedded in ATE phantom, exhibited a linear relation of 1/T2 versus pO2 for pO2 levels at 0, 7.6, 30, and 160 mmHg, with relative reading accuracy of about 10%. Conclusion The compact ESR scanner can report pO2 data in ATE phantom from an external position relative to the scanner. Implementing this scanner in preclinical and clinical applications for subcutaneous pO2 measurements is a feasible next phase for this development. This innovative design also has the potential to operate in conjunction with artificial skin graft for wound healing, combining therapeutic and pO2 diagnostic features.