Experimental study of the quantification of indocyanine green fluorescence in ischemic and non-ischemic anastomoses, using the SERGREEN software program

Abstract

Tissue ischemia is a key risk factor in anastomotic leak (AL). Indocyanine green (ICG) is widely used in colorectal surgery to define the segments with the best vascularization. In an experimental model, we present a new system for quantifying ICG fluorescence intensity, the SERGREEN software. Controlled experimental study with eight pigs. In the initial control stage, ICG fluorescence intensity was analyzed at the level of two anastomoses, in the right and in the left colon. Control images of the two segments were taken after ICG administration. The images were processed with the SERGREEN program. Then, in the experimental ischemia stage, the inferior mesenteric artery was sectioned at the level of the anastomosis of the left colon. Fifteen minutes after the section, sequential images of the two anastomoses were taken every 30 min for the following 2 h. At the control stage, the mean scores were 134.2 (95% CI 116.3-152.2) for the right colon and 147 (95% CI 134.7-159.3) for the left colon (p = 0.174) (Scale RGB-Red, Green, Blue). The right colon remained stable throughout the experiment. In the left colon, intensity fell by 47.9 points with respect to the pre-ischemia value (p < 0.01). After the first post-ischemia determination, the values of the ischemic left colon remained stable throughout the experiment. The relative decrease in ICG fluorescence intensity of the ischemic left colon was 32.6%. The SERGREEN program quantifies ICG fluorescence intensity in normal and ischemic situations and detects differences between them. A reduction in ICG fluorescence intensity of 32.6% or more was correlated with complete tissue ischemia.

Figure 1

Laparoscopic image in Spectra A + ICG mode of running suture manual end-to-end anastomosis of the right colon (1), without arterial manipulation, and of the left colon (2), without arterial manipulation.

Figure 2

(A) Evolution in images of the right colon after sectioning of the inferior mesenteric artery. Images are taken at 15, 45, 75, 105 and 135 min after the arterial section. Vascularization remains uniform over time. (B) Evolution in images of the left colon after sectioning of the inferior mesenteric artery. Images are taken at 15, 45, 75, 105 and 135 min after the arterial section. Ischemia remains uniform over time.

Figure 3

Ten areas of study of vascularization in the right colon (1) and in the left colon (2) using 10 × 10 pixel squares, highlighted in yellow circles. Predefined squares are applied over areas of uniform vascularization.

Figure 4

Boxplot showing the evolution over time from baseline prior to the section of the IMA to minute 135 after its section and that of the vein at the level of the right (1) and left (2) colon. The overlap of the two evolutions over time can be seen in graph 3, where the solid line represents right colon and the dashed line the left.