157 Real-time quantification of LSCI during intestinal laparoscopic surgery the mean intensity of the pixels in a window of 7x7 pixels. During the procedure, the surgeon was able to view live LSPU-values, as well as a graph plotting LSPU-values over time. For standardization purposes, the laparoscope was placed in a 3D-printed mount, 14 cm above the specimen, with the camera sensor placed perpendicular to the tissue. Data acquisition and statistical analysis LSPUs and lactate levels Four timepoints were selected to acquire data during the procedure. At T-1, prior to any manipulation of vascularization occurred, an LSCI recording of the untouched intestinal loops was made. Each loop was placed outside of the abdominal cavity on a black drape at the time of imaging for standardization purposes. During recording, lights in the operating room (OR) were turned off. Immediately after ligation of the arteries, the LSCI visualization mode was turned on and shown real-time to the operating surgeon (T0). Following a concise explanation on the system’s visualization of perfusion using a colour map, the surgeon designated four regions of interest (ROIs) accordingly: an ischemic area, a well-perfused area and two watershed areas (transition zones between well- and poorly perfused tissue; Figure 1).These ROIs were marked with a surgical tissue marker pen for reference during the image analysis. LSCI recording was repeated 60 (T60) and 120 (T120) minutes after devascularization. In addition to the LSCI recording, systemic lactate levels were taken at T0, T60 and T120 for every loop to estimate the ischemic state of the pig. Also, local capillary lactate (LCL) levels in the intestinal serosa were measured at the four ROIs. For practical reasons, this was done at T0 for the watershed and ischemic ROIs only in 3 loops, but in all loops for the well-perfused ROIs. At T60 and T120, LCL levels were taken at all four ROIs in all loops. The LCL measurement was done using a 23 Gauge needle and an EDGE lactate analyzer (ApexBio, Taipei, Taiwan, People’s Republic of China) which allowed for instant lactate measurements. Figure 1. Small bowel tissue was placed in an extracorporeal loop on black drape. At T0, arteries were ligated to induce ischemia. A) White light image as produced by a standard laparoscopic system. The mesenteric defect in the middle of the loop, is the result of cauterization of arterial vascularization. B) Visualization of perfusion levels in the same intestinal loop as seen by the surgeon during the procedure. Four regions of interest (ROIs) can be seen, representing the surgeon-selected perfusion areas: Well = well-perfused tissue (yellow); WS = watershed areas (red and green), Isch = ischemic tissue (blue). The scale bar on the left of the colourmap indicates the low flow (blue) to high flow (yellow) gradient. 8
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