(G-269) Wireless Diffuse Reflectance Spectroscopy for Noninvasive Assessment of Tissue Perfusion

Introduction:: Diffuse Reflectance Spectroscopy (DRS) is a non-invasive optical technique to assess tissue optical properties. A typical DRS system employs a fiber optic probe to deliver and collect light to/from tissue of interest at a distance. However, the use of fiber optic probes increases the manufacturing cost, imposes a risk of breakage, and limits in a certain clinical environment such as an operating room. To address this technical need, we propose a fiber-less, hand-held, wireless DRS system to estimate tissue oxygenation and total hemoglobin concentration

Materials and Methods:: We have developed a Monte Carlo look up table (MCLUT)-based inverse model to extract tissue optical properties from the measured reflectance with a commercial hand-held, wireless spectrometer. The ray-tracing software, ZEMAX was employed to model an optics geometry of a hand-held spectrometer, and run MC simulations over a wide range of absorption and reduced scattering coefficients mimicking biological tissues to build a LUT. We have verified our method in blood phantoms against the standard fiber-optic based DRS system (Fig.1). We have gradually deoxygenate the blood phantom while measuring it using both methods simultaneously. We also have performed a preclinical validation on a rat model of kidney ischemia.

Results, Conclusions, and Discussions:: The developed MCLUT-based inverse model fits the measured diffuse reflectance spectra with a hand-held spectrometer in a high accuracy (Fig.2a). The blood phantom results show that our fiber-less, hand-held DRS estimated tissue oxygenation has a high correlation ( > 0.9) with the tissue oxygenation values measured with the conventional fiberoptic-based DRS (Fig.2b). In a rat model, our proposed system shows the expected decrease of oxygenation level of kidney when clamping is applied. This study demonstrates that our proposed hand-held DRS system coupled with the devised MCLUT inverse model can accurately estimate tissue perfusion parameters. The complete wire- or fiber-less feature may promote the wider use of this DRS.

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