Optical coherence tomography and elastography for ex vivo visualization of early gastric cancer

Stomach (gastric) cancer survival depends significantly on the stage in which it is detected, and surveillance with white light endoscopy exhibits poor contrast between gastric cancer and healthy tissue, especially at early stages. Early gastric cancer can exhibit changes in epithelial microstructure, including loss of regular gastric pit structure and collagen alterations which increase tissue stiffness.

To improve contrast between early cancer and normal tissue, we investigate the use of optical coherence tomography (OCT) and elastography (OCE) to visualize changes in tissue structure and stiffness consistent with gastric cancer.

Images of eight samples of ex vivo human stomach tissue from three patients were collected with a benchtop OCT system. OCT was performed for qualitative visualization of tissue structure. OCE was then performed on 17 regions of interest using a simplified optical palpation method to extract relative stiffness measurements. A transparent silicone reference layer was placed on the tissue, and axial compression was applied. The resulting deformation (strain) of the reference layer was measured, and the corresponding stress applied to the sample surface was extracted from the characteristic stress-strain curve of the reference material. Spatially resolved stress measurements were mapped and overlaid on en face OCT images. Tissue classification was confirmed by pathology.

OCT image volumes showed more distinct gastric pit and tissue layer structure, as well as less optical attenuation, in normal tissue compared to gastric metaplasia and focal signet ring cell carcinoma (SRCC). Exemplary OCE-derived stress maps showed a trend of increasing measured stress with progression of precancer (metaplasia and dysplasia) and SRCC, suggesting increased tissue stiffness.

This proof-of-concept study provides evidence that OCT and OCE may be capable of visualizing differences in tissue structure and stiffness between normal, metaplastic, dysplastic, and early cancerous gastric tissue, potentially providing the basis for improved screening tools with higher sensitivity.