Optimizing Source Detector Separation for an Implantable Perfusion and Oxygenation Sensor
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Each year thousands of patients are added to the waiting list for liver transplants. The first 7-10 days after transplant have proven to be the most critical in patient recovery and it is hypothesized that monitoring organ vital signals in this period can increase patient and graft survival rates. An implantable sensor to monitor the organ perfusion and oxygenation signals following surgery is being developed by our group. The sensor operates based on measuring diffuse reflection from three light emitting diodes (735, 805 and 940 nm). In this work the optimal source detector spacing to maximize oxygenation signal level is investigated for a portal vein model. Monte Carlo simulations provided signal levels and corresponding penetration depths as a function of separation between a point optical source and detector. The modeling results indicated a rapid decay in the optical signal with increasing distance. Through further analysis, it was found that there exists an optimal range of point source to detector spacing, between roughly 1 and 2 mm, in which the blood signal from the simulated portal vein was maximized. Overall, these results are being used to guide the placement and configuration of our probe for in vivo animal studies.
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Optical Diagnostics and Sensing XI: Toward Point-of-Care Diagnostics; and Design and Performance Validation of Phantoms Used in Conjunction with Optical Measurement of Tissue III