## 3 Results
### Quantitative Parameters  
Of 22 patients, quantitative assessment was successful in 15, 22, 20, and 20 patients for OCT, SDF, LSCI, and FA, respectively. At the four locations (Loc1/Loc2/Loc3/Loc4), the number of obtained measurements for OCT were 12/10/8/10, for SDF 21/21/21/21, for LSCI 20/20/20/20, and for FA 17/20/20/18, respectively. The measurements for the SDF parameters were available in 21 patients at Loc4, except for MFI (\(n\) = 14). Comparing Loc1 with Loc4, a significant difference was noticed for 10 out of 14 parameters (Figure 2): the SDF parameters PVD, MFI, PPV, and velocity; the LSCI parameters Flux and \(\Delta\)%Flux; and the FA parameters influx time point, F\({}_{\text{max}}\), T\({}_{\text{1/2}}\), and mean slope. Of those, PVD, MFI, PPV, velocity, Flux, F\({}_{\text{max}}\), and mean slope decreased towards the fundus, while the \(\Delta\)%Flux, influx time point, and T\({}_{\text{1/2}}\) increased. No significant differences were noticed between the locations for the OCT parameter speckle %, the SDF parameters TVD and DBS, and the FA parameter T\({}_{\text{max}}\). Anastomotic leakage occurred in 4/22 patients (18.2%). Of the measurements available at Loc3, anastomotic leakage occurred in 1/8 (12.5%), 3/21 (14.3%), 4/20 (20.0%), and 2/20 (10.0%) for OCT, SDF, LSCI, and FA, respectively. No significant differences were observed for the quantitative parameters between the patients with or without anastomotic leakage at Loc3 (data not shown). Of the measurements available at Loc4, anastomotic leakage occurred in 1/10 (10.0%), 3/21 (14.3%), 4/20 (20.0%), and 2/18 (11.1%) for OCT, SDF, LSCI, and FA, respectively. A comparison of quantitative parameters at Loc4 between patients with and without anastomotic leakage is shown in Table 3. Of all the quantitative parameters, the FA values for the T\({}_{\text{1/2}}\) and mean slope significantly differed between patients with and without anastomotic leakage. The T\({}_{\text{1/2}}\) was 13.0 (total range 6.3-21.3) seconds in patients without anastomotic leakage, and increased to 29.3 (total range 27.8-30.8) seconds in the case of anastomotic leakage (\(p\) = 0.025). For T\({}_{\text{1/2}}\), the total range of values showed no overlap between patients with or without anastomotic leakage. The mean slope decreased from 1.3 (total range 0.1-11.0) to 0.2 (total range 0.1-0.2) in patients without and with anastomotic leakage (\(p\) = 0.041), respectively. All the values for the SDF parameters and for Flux were non-significantly higher (Table 3). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Field of View** & **Depth-Resolving** & **Ease of Use** & **Real-Time** & **Practical Limitations** \\ \hline
**OCT** & 10 mm \(\times\) 10 mm \(\times\) 25 mm & + & \
\begin{tabular}{c} Sterile sheet, \\ probe handling \\ \end{tabular} & + &
\begin{tabular}{c} Motion artefacts, \\ shadowing \\ \end{tabular} \\ \hline
**SDF** & 1 mm \(\times\) 1 mm & - &
\begin{tabular}{c} Sterile sheet, \\ tissue-contact \\ \end{tabular} & + & Motion artefacts, focus \\ \hline
**LSCI** &
\begin{tabular}{c} Wide-field \\ ROI: \(\bullet\) 1 cm \\ \end{tabular} & - & Non-contact & + & OR lights off \\ \hline
**FA** & \
\begin{tabular}{c} Wide-field \\ ROI: \(\bullet\) 1 cm \\ \end{tabular} & - & Non-contact & + &
\begin{tabular}{c} Invasive (ICG injection), \\ OR lights off \({}^{*}\) \\ \end{tabular} \\ \hline \hline \end{tabular}  
* FA Fluorescence Angiography, ICG Indocyanine Green, LSCI Laser Speckle Contrast Imaging, OCT Optical Coherence Tomography, OR Operating Room, ROI Region-of-interest, SDF Sidestream Darkfield Microscopy.
* Not when used laparoscopically  
\end{table} 
Table 2: Imaging characteristics. Figure 2: Fourteen quantitative parameters at four locations of the gastric conduit. Data are shown as medians and interquartile ranges. _p_-value is shown for the difference between Loc1 and Loc4. OCT Optical Coherence Tomography: Speckle in %.