Feasibility of Optical Coherence Tomography (OCT) for Intra-Operative Detection of Blood Flow during Gastric Tube Reconstruction

Abstract

In this study; an OCT-based intra-operative imaging method for blood flow detection during esophagectomy with gastric tube reconstruction is investigated. Change in perfusion of the gastric tube tissue can lead to ischemia; with a high morbidity and mortality as a result. Anastomotic leakage (incidence 5⁻20%) is one of the most severe complications after esophagectomy with gastric tube reconstruction. Optical imaging techniques provide for minimal-invasive and real-time visualization tools that can be used in intraoperative settings. By implementing an optical technique for blood flow detection during surgery; perfusion can be imaged and quantified and; if needed; perfusion can be improved by either a surgical intervention or the administration of medication. The feasibility of imaging gastric microcirculation in vivo using optical coherence tomography (OCT) during surgery of patients with esophageal cancer by visualizing blood flow based on the speckle contrast from M-mode OCT images is studied. The percentage of pixels exhibiting a speckle contrast value indicative of flow was quantified to serve as an objective parameter to assess blood flow at 4 locations on the reconstructed gastric tube. Here; it was shown that OCT can be used for direct blood flow imaging during surgery and may therefore aid in improving surgical outcomes for patients.

Keywords: OCT; esophagectomy; flow; gastric tube; monitoring; optical imaging; perfusion; speckle; surgery.

Figure 1

Esophageal cancer with gastric vascularization, esophagectomy and gastric tube reconstruction with only one artery left (gastroepiploic artery).

Figure 2

Santec OCT system (panel A), schematic figure (panel B) of gastric tube with ROI of 10 × 10 mm of OCT grayscale images at four perfusion areas, with shadowing of vessels in cross sectional OCT image (panel C).

Figure 3

Data analysis steps of OCT M-mode scans, all images are shown from the y-z plane. (a) grayscale y-z M-mode scan; (b) applied dB mask to exclude noise from the data, the white areas on this image are included as data (c) over the time scale calculated speckle contrast values (of regions of included data after the dB threshold (d) speckle contrast within the 0.42–0.62 gate plotted in white (e) speckle contrast after applying a median filter with a 7 × 3 pixel kernel (f) gated and filtered speckle contrast (red) overlaid with the grayscale OCT image.

Figure 4

Flow diagram: patient and data inclusion.

Figure 5

3D OCT scan of the gastric tube, (a) volumetric representation (b) with cross section visualized.

Figure 6

OCT B-scan of location 4, the fundus (at the left panel), and HE stained histology slide (the right panel) obtained at the end of the gastric tube. Blood and lymph vessels are indicated in red and yellow, respectively. The corresponding tissue layers, serosa, subserosa (purple/dark pink) and muscularis propria (light pink) are depicted in both panels. The scale bar depicts a length of 1 mm.

Figure 7

Single M-mode OCT scans (left) and the corresponding calculated contrast (right) of a. a static region of the flow phantom, b. a region with flow in the flow phantom in which the red line depicts the approximated location of the top of the flow channel, c. a static region of tissue and d. a region with flow in tissue by a blood vessel at approximately 0.2 mm below the tissue surface. The red bar depicts the speckle contrast threshold used in this manuscript.

Figure 8

Normalized percentage of pixels per patient per location obtained from the OCT M-mode scans. The values are normalized relative to location 1, hence only the plots for patients with a value for location 1 are shown.

Figure 9

OCT speckle contrast indicative of flow overlaid with OCT grayscale (YZ) images from M-mode scans from location 1 (L1, 3 cm below the watershed), location 2 (L2, watershed), location 3 (L3, 3 cm above the watershed), location 4 (L4, fundus). In patient 9 high speckle contrast indicative of flow is seen in location 2 on the watershed area. In patient 14 and 19 a decreased speckle contrast indicative of flow is observed towards location 4. In patient 17 an increase in speckle contrast indicative of flow from location 1 to 4 is observed.

Figure 9

OCT speckle contrast indicative of flow overlaid with OCT grayscale (YZ) images from M-mode scans from location 1 (L1, 3 cm below the watershed), location 2 (L2, watershed), location 3 (L3, 3 cm above the watershed), location 4 (L4, fundus). In patient 9 high speckle contrast indicative of flow is seen in location 2 on the watershed area. In patient 14 and 19 a decreased speckle contrast indicative of flow is observed towards location 4. In patient 17 an increase in speckle contrast indicative of flow from location 1 to 4 is observed.

Figure 10

OCT scan of location 4 (fundus), the scale bar depicts a length of 1 mm, and histology slides HE-stained, of patient 14, 17 and 19 with blood vessels in red and tissue layers: serosa, subserosa (purple/dark pink), muscularis propria (light pink).