Intraoperative reperfusion assessment of human pancreas allografts using hyperspectral imaging (HSI)

Abstract

Background: The most common causes of early graft loss in pancreas transplantation are insufficient blood supply and leakage of the intestinal anastomosis. Therefore, it is critical to monitor graft perfusion and oxygenation during the early post-transplant period. The goal of our pilot study was to evaluate the utility of hyperspectral imaging (HSI) in monitoring the microcirculation of the graft and adequate perfusion of the intestinal anastomosis during pancreatic allotransplantation.

Methods: We imaged pancreatic grafts and intestinal anastomosis in real-time in three consecutive, simultaneous pancreas-kidney transplantations using the TIVITA^® HSI system. Further, the intraoperative oxygen saturation (StO₂), tissue perfusion (near-infrared perfusion index, NIR), organ hemoglobin index (OHI), and tissue water index (TWI) were measured 15 minutes after reperfusion by HSI.

Results: All pancreas grafts showed a high and homogeneous StO₂ (92.6%±10.45%). Intraoperative HSI analysis of the intestinal anastomosis displayed significant differences of StO₂ (graft duodenum 67.46%±5.60% vs. recipient jejunum: 75.93%±4.71%, P<0.001) and TWI {graft duodenum: 0.63±0.09 [I (Index)] vs. recipient jejunum: 0.72±0.09 [I], P<0.001}. NIR and OHI did not display remarkable differences {NIR duodenum: 0.68±0.06 [I] vs. NIR jejunum: 0.69±0.04 [I], P=0.747; OHI duodenum: 0.70±0.12 [I] vs. OHI jejunum: 0.68±0.13 [I], P=0.449}. All 3 patients had an uneventful postoperative course with one displaying a Banff 1a rejection which was responsive to steroid treatment.

Conclusions: Our study shows that contact-free HSI has potential utility as a novel tool for real-time monitoring of human pancreatic grafts after reperfusion, which could improve the outcome of pancreas transplantation. Further investigations are required to determine the predictive value of intraoperative HSI imaging.

Keywords: Hyperspectral imaging (HSI); intraoperative imaging; pancreas transplantation.

Figure 1

Hyperspectral imaging (HSI) with the TIVITA^® hyperspectral camera system. (A) Schematic drawing of hyperspectral image acquisition. The tissue under investigation (object) gets illuminated by a light source. The reflected light from the tissue is captured by the objective lens [1] and focused to the entrance slit [2] of the spectrograph. A disperse device [3-5] inside the spectrograph, consisting of special lenses [3 and 5] and a transmission grating [4] splits the light into several beams depending on the wavelength. Finally, an image sensor [6] for digital processing captures these beams. (B) TIVITA^® (Diaspective Vision) device that is mounted on a mobile cart with light source and hyperspectral camera system attached to a holding arm. During HSI the spectrograph inside the camera is moved over the image plane by an integrated motor to scan the whole object. The false-color imaging procedure is calculated with the attached computer and visualized on a monitor.

Figure 2

Hyperspectral images and tissue parameters of the pancreas graft after reperfusion. Representative intraoperative (A) RBG image, and corresponding hyperspectral imaging (HSI) generated (B) color coded oxygen saturation (StO₂), (C) near-infrared perfusion (NIR), (D) organ hemoglobin index (OHI), and (E) tissue water index (TWI) 15 minutes after reperfusion of the pancreas graft. Three standardized markers, were placed on pancreas head, body and tail to evaluate the tissue perfusion. (F) Mean absorbance spectra/distribution of pancreatic tissue parameters. All data are presented as the mean ± SD (n=3).

Figure 3

Hyperspectral images and tissue parameters of the intestinal anastomosis during pancreas transplantation. Representative intraoperative (A, J = jejunum; D = duodenum) RBG image and corresponding hyperspectral imaging (HSI) generated (B) color coded oxygen saturation (StO₂), (C) near-infrared perfusion (NIR), (D) organ hemoglobin index (OHI), and (E) tissue water index (TWI) of the intestinal anastomosis. Two markers, standardized in site, were placed on the duodenum of the graft and the recipients’ jejunum to evaluate the tissue perfusion. (F) Comparison of tissue parameters of the intestinal anastomosis. All data are presented as the mean ± SD (n=3).