107 Simultaneous fluorescence imaging of bowel perfusion and ureter delineation using methylene blue and remained clearly visible until the end of every experiment (Figure 2). For the surgical team, no visual differences between the higher, middle, or lower doses were seen during the experiments. All evaluations showed a persistent clear delineation of the ureters in NIRF mode. The fluorescence signal was maximal during peristaltic contractions of the ureter. TBR values of all left ureters (except for pig no. 4, right ureter) at different time points are summarized in Table 2. The highest measured TBR was 8.89. All details about the mixed model analysis are presented in Table 3. Univariate tests did not show a significant difference when comparing the three dose groups (p = 0.345). The mean TBR value was the highest in group 2 (5.21 ± 0.37). The latter was confirmed in pairwise comparisons, which showed group 2 differed the most in mean TBR value compared to both other groups. The mean difference was 0.745 (p = 0.250) and 0.833 (p = 0.209) compared to group 1 and group 3, respectively. The relation between group and time was not significant (p = 0.855), indicating that the group effect did not significantly differ at different time points. As a consequence, the group effect was computed over all time points and showed non-significant effect either. No adverse reactions were observed in any of the animals after MB injection. In the first pig, the left ureter was purposely transected at the end of the experiment. The leakage of urine due to ureteral damage could be clearly visualized with the NIRF imaging system (Supplementary, Figure A). Table 2. TBR values for different time points Ureter MB dose Pig 1 Left 0.75mg/kg Pig 2 Left 0.75mg/kg Pig 3 Left 0.50mg/kg Pig 4 Right 0.50mg/kg Pig 5 Left 0.25mg/kg Pig 6 Left 0.25mg/kg TBR 5 1.32 ± 0.12 1.18 ± 0.14 0.87 ± 0.25 0.96 ± 0.25 0.91 ± 0.23 2.98 ± 0.22 TBR 10 4.61 ± 0.35 5.70 ± 0.45 3.00 ± 0.29 5.61 ± 0.52 1.00 ± 0.16 5.89 ± 0.28 TBR 20 4.96 ± 0.41 3.95 ± 0.45 5.02 ± 0.37 7.88 ± 0.62 2.42 ± 0.28 5.98 ± 0.90 TBR 30 6.00 ± 0.15 4.08 ± 0.62 7.00 ± 0.34 5.35 ± 0.61 1.08 ± 0.43 4.76 ± 0.44 TBR 40 5.45 ± 0.31 3.51 ± 0.33 7.94 ± 0.35 4.34 ± 0.57 6.39 ± 0.44 - TBR 50 4.29 ± 0.27 3.92 ± 0.36 5.75 ± 0.39 7.04 ± 0.59 4.47 ± 0.58 5.06 ± 0.26 TBR 60 4.46 ± 0.21 4.27 ± 0.50 6.42 ± 0.31 6.11 ± 0.51 6.41 ± 0.73 7.10 ± 0.57 TBR 80 6.58 ± 0.37 3.94 ± 0.41 8.89 ± 0.89 3.20 ± 0.38 3.69 ± 0.35 4.67 ± 0.33 TBR 100 3.97 ± 0.25 4.21 ± 0.49 4.63 ± 0.50 5.59 ± 0.46 7.51 ± 0.54 2.61 ± 0.31 TBR 120 7.02 ± 0.68 4.17 ± 0.50 3.86 ± 0.45 4.71 ± 0.34 8.84 ± 0.65 4.09 ± 0.32 TBR 180 - 2.60 ± 0.41 - 4.18 ± 0.37 - - TBR 240 5.51 ± 0.42 2.66 ± 0.24 5.46 ± 0.52 6.69 ± 0.68 - - TBR 360 - - 3.86 ± 0.28 - - 2.48 ± 0.20 TBR 420 4.36 ± 0.36 - - - - - TBR, Target to Background ratio. 5
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