Quantitative Fluorescence Imaging of Perfusion-An Algorithm to Predict Anastomotic Leakage

Abstract

This study tests fluorescence imaging-derived quantitative parameters for perfusion evaluation of the gastric tube during surgery and correlates these parameters with patient outcomes in terms of anastomotic leakage. Poor fundus perfusion is seen as a major factor for the development of anastomotic leakage and strictures. Fluorescence perfusion imaging may reduce the incidence of complications. Parameters for the quantification of the fluorescence signal are still lacking. Quantitative parameters in terms of maximal intensity, mean slope and influx timepoint were tested for significant differences between four perfusion areas of the gastric tube in 22 patients with a repeated ANOVA test. These parameters were compared with patient outcomes. Maximal intensity, mean slope and influx timepoint were significantly different between the base of the gastric tube and the fundus (p < 0.0001). Patients who developed anastomotic leakage showed a mean slope of almost 0 in Location 4. The distance of the demarcation of ICG to the fundus was significantly higher in the three patients who developed anastomotic leakage (p < 0.0001). This study presents quantitative intra-operative perfusion imaging with fluorescence. Quantification of the fluorescence signal allows for early risk stratification of necrosis.

Keywords: anastomosis; fluorescence imaging; parameters; perfusion; surgery.

Figure 1

Schematic image of fluorence imaging set-up with two light sources, NIR camera and colour video camera, and ICG injection [16].

Figure 2

Combined fluorescence and white light image of a gastric tube during surgery with influx of ICG (A). In Panel (B) a greyscale image of the gastric tube is shown with the four perfusion areas selected in circles with 300 pixels with #1 = 3 cm below the watershed, #2 = watershed, #3 = 3 cm above the watershed and #4 = fundus. In both pictures the sterile gauze (red triangle) is indicating the watershed (end of the right gastroepiploic artery) and the metric ruler is placed in the FOV for pixel calibration (scalebar = 1 mm). Panel (C) shows the temporal fluorescence imaging intensity traces for the 4 locations with the colored arrows indicating the automatically detected influx timepoints (arrows) of the curves. Colored areas indicate the 10 s interval.

Figure 3

Panel (A–D) show the point-wise derivative curves of the four intensity traces as a function of time at location #1 (dark blue) (A), #2 (green) (B), #3 (red) (C) and #4 (light blue) (D), with colors indicating the corresponding fluorescence trace in Figure 2.

Figure 4

Flow diagram of patient inclusion.

Figure 5

Fluorescence image of the gastric tube during surgery with the overlay image (A), the near infrared image at the influx timepoint of ICG (τ), clearly depicting the arteries (B). After influx in the arteries, perfusion of the microvascular network (yellow arrows) is visible in the NIR image (C) τ + 10 s. The sterile gauze indicates the watershed. Upper scale of the metric ruler is in cm.

Figure 6

Panel (A): Maximal intensity F_max of ICG and Panel (B): mean slope of fluorescence intensity over time (F_slope) measured with the custom-made software at the four perfusion areas. Panel (C): Mean slope of fluorescence intensity at Location 4 for patients who developed leakage (3) versus patients without leakage (17). F_slope was <0.2 in patients who developed leakage. Panel (D): Influx timepoint (τ) in seconds of all patients with Location 1 imaged (n = 16). Panel (E): Measured distance between demarcation of ICG and fundus in cm, differences are shown between the patients with leakage (n = 3) and the non-leakage group (n = 17). The distance was smaller in the non-leakage group (p = 0.0005). Panel (F): Measured distance of the watershed area (selected by the surgeon based on arterial pulse and visualization, pointed out with a sterile gauze) in cm. No significant differences were present between the leakage group and non-leakage group (p = 0.30). Data in all patients are presented in boxplots with median, interquartile ranges and maximum and minimum values.

Figure 6

Panel (A): Maximal intensity F_max of ICG and Panel (B): mean slope of fluorescence intensity over time (F_slope) measured with the custom-made software at the four perfusion areas. Panel (C): Mean slope of fluorescence intensity at Location 4 for patients who developed leakage (3) versus patients without leakage (17). F_slope was <0.2 in patients who developed leakage. Panel (D): Influx timepoint (τ) in seconds of all patients with Location 1 imaged (n = 16). Panel (E): Measured distance between demarcation of ICG and fundus in cm, differences are shown between the patients with leakage (n = 3) and the non-leakage group (n = 17). The distance was smaller in the non-leakage group (p = 0.0005). Panel (F): Measured distance of the watershed area (selected by the surgeon based on arterial pulse and visualization, pointed out with a sterile gauze) in cm. No significant differences were present between the leakage group and non-leakage group (p = 0.30). Data in all patients are presented in boxplots with median, interquartile ranges and maximum and minimum values.