Intraoperative spectral imaging versus ICG fluorescence for gastric conduit viability in esophagectomy

Anastomotic leakage remains a critical complication following esophagectomy, occurring in 8-20% of patients. While indocyanine green fluorescence imaging (ICG-FI) is commonly used to assess perfusion, it requires dye injection and does not directly measure tissue metabolism. This study evaluates a real-time, contrast-free spectral imaging (SI) system for quantifying gastric conduit oxygenation ( ${\mathrm{StO}}_2$ ) and compares its performance to ICG-FI.

Intraoperative SI was successfully performed in 33 patients undergoing laparoscopic Ivor Lewis esophagectomy using a video-rate snapshot spectral camera, acquiring 16 spectral bands in the 460-600 nm range. A deep learning model estimated ${\mathrm{StO}}_2$ of the gastric conduit and quantitative perfusion metrics were derived from ICG-FI time-intensity curves. Local capillary lactate levels were measured as a physiological reference for tissue hypoxia. Statistical analyses compared ${\mathrm{StO}}_2$ and ICG-FI metrics.

SI successfully differentiated well-perfused from ischemic tissue (median ${\mathrm{StO}}_2$ : $69.16\%$ vs. $31.58\%$ , p < 0.001). The estimated ${\mathrm{StO}}_2$ showed a strong negative correlation with local capillary lactate (r=-0.72, p < 0.001). While quantitative ICG-FI metrics ( $T_{1/2}$ and ${\mathrm{AUC}}_{50\%}$ ) revealed significantly reduced perfusion at the anastomosis site compared to well-perfused tissue (p < 0.001), they showed only a moderate correlation with ${\mathrm{StO}}_2$ (r=0.50, p < 0.001). Notably, in a patient who developed anastomotic leakage, both modalities detected ischemia intraoperatively, but they show different transition borders, with SI indicating a more extensive hypoxic area than ICG-FI.

Snapshot SI provides a real-time, objective assessment of tissue oxygenation without the need for contrast agents. Its strong correlation with lactate suggests it may offer potential complementary value to dye-based perfusion imaging, potentially improving anastomotic site selection, although outcome-based validation studies in larger cohorts are needed.