Liohai Chen, PhD, Roberto Bustos, MD, Valentina Valle, MD, Gabriela Aguiluz, MD, Xiwei Hao, Antonio Gangemi, MD, Pier C Giulianotti, MD, FACS. University of Illinois at Chicago
Objective: Alteration in perfusion is a major biomarker to indicate the function of an injured, resected or transplanted organ. Currently, tissue perfusion and viability are estimated from the tissue color, the presence of peristalsis, pulsation or bleeding. This can be very subjective and based on the experience of the surgeon. Indocyanine green (ICG) fluorescence imaging has been commonly used for assessing tissue perfusion. However, the half-life of ICG in blood circulation, which is only 3–5 minutes, prevents its application for monitoring the perfusion continuously. On the other hand, bright-field imaging is performed all the time in laparoscopic or robotic surgery, as it essentially functions as the eyes for the surgeon to view the tissue anatomy. The objective of the study is to explore the use of bright-field endoscope images/videos to assess the tissue perfusion/viability continuously without the involvement of expensive instrumentation, or extensive patient manipulations in the operating room.
Description of the method: In order to assess the tissue perfusion using bright-field imaging, a mixture of blue light (~ 450nm) and red light (~ 630nm) was used for illuminating the tissue. Since the oxygenated blood and deoxygenated blood exhibit similar absorptions in 400-580 nm range, but display a great absorption difference in 600 – 680nm range, backscattered contrast of the tissues with different concentrations of oxygenated and deoxygenated blood can be generated under the illumination of mixed light. The intensity difference of backscattered light in 630 nm and 450nm was mathematically correlated with the exponent of oxygenated blood concentration under the modified Beer's law. The tissue oxygenation maps were generated by 1) separating the red and blue components of the bright-field images; 2) subtracting the intensity of blue component from the red component, and 3) conducting an exponential transformation. The contrast in the resulting image indicated the oxygenation status of the tissue.
Preliminary results: A porcine model that had controllable small bowel ischemic segments was created by hanging a small bowel loop transparietally (tied extracorporeally) and selectively transecting the arteries feeding the segment. By analyzing the bright-field images/videos using the above-mentioned algorithm, a tissue oxygenation map was created. The ratio of contrast between the well-perfused and ill-perfused areas in the oxygenation map matched the steady state ICG fluorescence intensity in these segments. The difference between tissue oxygenation rate, extracted from the bright field video frames, and tissue perfusion rate, determined by the dynamics of ICG fluorescence intensity, upon unclamping the arteries were quantified to indicate the tissue oxygen consumption rate (viability).
Conclusion: A mathematic model and algorithm were developed to extract the tissue oxygenation information from bright-field images and videos. Combining with ICG florescence videography, perfusion and tissue metabolism activities can be assessed via quantifying the oxygen consumption rate during an in-situ reactive hyperemia process. While a more comprehensive study is needed, the proposed method has the potential to measure the tissue viability during surgery.
Presented at the SAGES 2017 Annual Meeting in Houston, TX.
Abstract ID: 98902
Program Number: ETP752
Presentation Session: Emerging Technology Poster Session (Non CME)
Presentation Type: Poster
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