19 March 2015 A hand-held EPR scanner for transcutaneous oximetry
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Abstract
Cutaneous (skin) oxygenation is an important prognostic factor for the treatment of chronic wounds, skin cancer, diabetes side effects, and limb amputation. Currently, there are no reliable methods for measuring this parameter. Oximetry, using electron paramagnetic resonance (EPR) spectroscopy, is emerging as a potential tool for clinical oximetry, including cutaneous applications. The problem with EPR oximetry, however, is that the conventional EPR design requires the use of a large magnet that can generate homogeneous field across the sample, making it unattractive for clinical practice. We present a novel approach that makes use of a miniature permanent magnet, combined with a small microwave resonator, to enable the acquisition of EPR signals from paramagnetic species placed on the skin. The instrumentation consists of a hand-held, modular, cylindrical probehead with overall dimensions of 36-mm diameter and 24-mm height, with 150-g weight. The probehead includes a Halbach array of 16 pieces (4×4×8 mm3) of Sm-Co permanent magnet and a loop-gap resonator (2.24 GHz). Preliminary measurements using a Hahn-echo pulse sequence (800 echos in 20 ms) showed a signalto- noise ratio of ~70 compared to ~435 in a homogenous magnet under identical settings. Further work is in progress to improve the performance of the probehead and to optimize the hand-held system for clinical use
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Helen Wolfson, Rizwan Ahmad, Ygal Twig, Aharon Blank, Periannan Kuppusamy, "A hand-held EPR scanner for transcutaneous oximetry", Proc. SPIE 9417, Medical Imaging 2015: Biomedical Applications in Molecular, Structural, and Functional Imaging, 941706 (19 March 2015); doi: 10.1117/12.2083864; https://doi.org/10.1117/12.2083864
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