Hyperspectral abdominal laparoscopy with real-time quantitative tissue oxygenation imaging: a live porcine study

Abstract

Background: Ischaemia is a critical complication, and can result in poor surgical outcomes. While intra-operative overt ischaemia can be perceived with the naked eye, timely recognition of borderline perfusion can prevent post-operative ischaemic complications, which is particularly relevant for colorectal anastomoses. Consequently, there is a clinical need for new technologies to intra-operatively assess tissue oxygenation (indicative of end organ perfusion), with minimal disruption to the surgical workflow. Here we present a hyperspectral imaging (HSI) system for laparoscopic surgery. This system provides live, easy to interpret, tissue oxygenation (StO₂) maps with associated quantitative values.

Methods: White light view and tissue oxygenation maps were reconstructed from a protoype laparoscopic Hyperspectral Surgical System (HSS). First, in a live porcine model (55 kg female), the mesentery of a small bowel loop was temporarily occluded with a laparoscopic grasper, then released whilst being imaged with HSI. The quantitative StO₂ values obtained from the HSS were compared with those of a non-invasive tissue oximetry probe (Moor VMS-Oxy, Moor Instruments Ltd, United Kingdom). Secondly, mimicking a laparoscopic colon resection and anastomosis, the colorectal junction was mobilised laparoscopically, exteriorised, transected, anastomosed and repositioned in the abdominal cavity. In order to compare healthy and ischaemic colon, the distal part was intentionally devascularised. Tissue oxygenation maps were compared with indocyanine green fluorescence angiography (ICG-FA) of the anastomotic region.

Results: The HSS was used as the primary scope to complete a laparoscopic colorectal anastomosis, providing a simultaneous white light view and hyperspectral information. Quantitative results from small bowel imaging were shown to correlate with measurements from the superficial tissue oximetry probe. Real-time tissue oxygenation maps were shown to visually correlate with ICG-FA.

Conclusion: The HSS can guide laparoscopic surgical procedures whilst providing visual and quantitative tissue oxygenation information in a live animal model. This paves the way for further studies to assess clinical applications.

Keywords: StO2; anastomosis; hyperspectral imaging; laparoscopy; minimally invasive surgery; tissue oxygenation.

Figure 1

(Left) Simple 2D white light image. (Middle) 3D (two spatial: $\chi ,\gamma$ and one spectral: $\lambda$) HSI image, resulting in a complete hypercube. (Right) Schematic representation of a HSI generated spectral curve from defined region of interest.

Figure 2

Tissue oximetry probe secured to a Johan laparoscopic grasper and passed via a 12 mm laparoscopic port.

Figure 3

(A) Small bowel with open grasper and mesentery not occluded in RGB. (B) Small bowel with mesentery not occluded in StO₂ vision. (C) Small bowel with closed grasper and mesentery occluded in RGB. (D) Small bowel with mesentery occluded in StO2 vision. Tissue oxygenation map colour bar denotes areas corresponding to low and high StO₂. White square denotes the region at which the tissue oximetry probe was placed to generate the graph seen in Figure 4.

Figure 4

(A) tissue oximetry probe readings from well perfused (WP) small bowel (phase i), during induced ischaemia and reperfusion (phase iii) and following reperfusion (phase v). Dotted lines represent the clamping (phase ii) and release (phase iv) of the small bowel mesentery, during which no StO₂ data could be recorded because the HSS light source was switched on for visualisation of the grasper. (B) HSS generated quantitative StO₂ readings from well perfused (WP) small bowel (phase i), during induced ischaemia (phase iii) and reperfusion of the small bowel (phase v). Dotted lines represent the time points where the small bowel mesentery was occluded and released.

Figure 5

Comparison of ischaemic rectum and well perfused colon. (A) HSI-generated RGB. (B) Near-infrared (NIR) enabled laparoscope RGB. (C) HSI-generated StO₂ map. (D) NIR overlay of the same anastomotic region. Different viewpoints of the anastomosis are due to imaging via different ports to accommodate both the HSS and laparoscope (Ele Vision).

Figure 6

Use of the HSS for laparoscopic surgery. It simultaneously provides the RGB view generated from hyperspectral information (left on the display monitor) as well as the StO₂ colour map display (right on the display monitor). The image displayed on the screen has been replaced to better represent the visualised StO₂ map.