163 Real-time quantification of LSCI during intestinal laparoscopic surgery Cut-off values Logarithmic curve estimation between LSPUs and LCL showed an R2 of 0.56. A scatterplot of all ROIs from ischemic and well-perfused tissue with the coefficient can be found in Figure 5. The cut-off value for LSPUs was determined at 69 AU with a sensitivity of 0.94 and specificity of 0.87 (Youden index 0.81). Consecutively, a cut-off value of 3.8 mmol/L was calculated for lactate, with a sensitivity of 0.97 and specificity of 1.00 (Youden index 0.97). Figure 5. Scatterplot of Regions of Interest (ROIs) from ischemic (blue) and well-perfused (yellow) areas. Higher values indicate better perfusion. The horizontal black dashed line represents the cut-off value for lactate levels (3.8mmol/L), whereas the vertical dotted line represents the cutoff value for LSPUs (69 AU). In addition, logarithmic curve estimation was used to estimate an R2-value of 0.56 (solid black curve). A difference can be noticed between ischemic values and well-perfused values, as higher LSPUs are linked with lower lactate levels. Inter-observer variability All images were assessed by all experienced and non-experienced observers. No significant differences were observed between the groups regarding the time taken to point out a ROI. Experts failed to place one ROI in 17 cases (3.3%), and physicians in 12 instances (2.3%), citing indistinct transitions between well-perfused and ischemic tissue or broad gradients from high (yellow) to low (blue) values. Both experts and physicians showed similar decision making. A dot plot of all measurements is presented in Figure 6. When tasked with identifying watershed areas, 66.3% of both experts and physicians placed the ROI more towards the ischemic side (average of 0.54 cm [IQR 0.26-1.41] and 0.66 cm [IQR 0.33-1.29] respectively), compared to the operating surgeon. A site towards better perfused tissue was chosen by 33.5% of experts and 33.7% of physicians (average of 0.44 cm [IQR 1.18-0.18] and 0.45 cm [IQR 1.11-0.18] respectively). When comparing the placement of all ROIs to that of the operating surgeon, 72% of ROIs were located within one centimeter, whether proximal or distal. In observations within a two 8
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