Perfusion and Oxygenation Optical Sensor

Dysfunction of implanted organs can be life threatening and leads to a considerable loss of grafts. Advancement in medical procedures has helped increase the success rates of organ transplant surgeries; however, there is an extensive need of tools to monitor the function of the implanted organ post-surgery. Vascular anastomoses, especially thrombosis in blood microvessels, account for a large number of transplanted organ dysfunction. A device that can detect these anastomoses early saves grafts and decreases the risk on patients with newly transplanted organs. Our lab, in collaboration with Oak Ridge National Laboratory and University of Pittsburgh, has designed an implantable optical sensor that can monitor blood perfusion and oxygenation in blood micro-vessels. The sensor delivers and monitors light at three different wavelengths in the red and infrared region (705, 810, and 940 nm) where the light penetration in tissue is on the order of millimeters. The absorption coefficients of hemoglobin for the 705 and 940 nm wavelengths vary according to blood oxygenation levels. The 810 nm light is near the isobestic point and thus the corresponding absorption coefficient is unaltered by the blood oxygen level. This last wavelength is used to distinguish between changes due to oxygenation in the blood versus changes due to perfusion.

Schematic of implanted sensor (1).	Monte Carlo simulation of three wavelengths of light (705, 810, and 940 nm) propagating through liver tissue at various oxygenation levels (2).

Note: All pictures were obtained from the reference below.

Collaborators:

Dr. Mark Wilson, University of Pittsburgh, Department of Surgery 

Dr. Nance Ericson, Oak Ridge National Laboratory, Engineering Science & Tech. Division

References:

(1) Ericson, M. N., Wilson, M. A., Coté, G. L., Baba, J. S., Xu, W., Bobrek, M., Britton, C. L., Hileman, M. S., Moore, M.
R., Emery, M. S. and Lenarduzzi, R. (2004) "Implantable sensor for blood flow monitoring after transplant surgery", Minimally Invasive Therapy and Allied Technologies, 13:2, 87 — 94

(2) Ibey, B., S. Lee, et al. (2004). "Modeling of a three-source perfusion and blood oxygenation sencor for transplant monitoring using Multi-Layer Monte Carlo code." Proceeding of SPIE. Vol 5325 (62).

 

For more information, contact Tony Akl