Background. Hyperspectral imaging (HSI) is a relatively new method used in image-26 guided and precision surgery, which has shown promising results for characterization 27 of tissues and assessment of physiologic tissue parameters. Previous methods used 28 for analysis of preconditioning concepts in patients and animal models have shown 29 several limitations of application. The aim of this study was to evaluate HSI for the 30 measurement of ischemic conditioning effects during esophagectomy. 31 Methods. Intraoperative hyperspectral images of the gastric tube through the mini-32 thoracotomy were recorded from n=22 patients, 14 of whom underwent laparoscopic 33 gastrolysis and ischemic conditioning of the stomach with two-step transthoracic 34 esophagectomy and gastric pull-up with intrathoracic anastomosis after 3-7 days. 35 The tip of the gastric tube (later esophago-gastric anastomosis) was measured with 36 HSI. Analysis software provides a RGB image and 4 false color images representing 37 physiologic parameters of the recorded tissue area intraoperatively. These parameters contain tissue oxygenation (StO2), perfusion-(NIR Perfusion Index), 1 organ hemoglobin-(OHI) and tissue water index (TWI). 2 Results. Intraoperative HSI of the gastric conduit was possible in all patients and did 3 not prolong the regular operative procedure due to its quick applicability. In particular, 4 the tissue oxygenation of the gastric conduit was significantly higher in patients who 5 underwent ischemic conditioning (StO2Precond. = 78%; StO2NoPrecond. = 66%; p = 0.03). Conclusions. HSI is suitable for contact-free, non-invasive and intraoperative 7 evaluation of physiological tissue parameters within gastric conduits. Therefore HSI is 8 a valuable method for evaluating ischemic conditioning effects and may contribute to 9 reduce anastomotic complications. Additional studies are needed to establish normal 10 values and thresholds of the presented parameters for the gastric conduit 11 anastomotic site.

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The HSI method provides a non-contact, non-invasive, intraoperative imaging procedure without the use of a contrast medium, which enables a real-time analysis of physiological anastomotic parameters, which may contribute to determine the "ideal" anastomotic region. In light of this, the establishment of this methodology in the field of visceral surgery, enabling the generation of normal or cut off values for different gastrointestinal anastomotic types, is an obvious necessity.

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