Dynamic holographic endoscopy—ex vivo investigations of malignant tumors in the human stomach

Laser holographic interferometry is based on the superimposition of the holograms of different motional states of an object on a single holographic storing medium. Using a combination of holographic interferometry and endoscopic imaging, we tried to detect areas of focally disturbed tissue elasticity in gastric cancer preparations. By connecting a mobile electronic speckle pattern interferometry (ESPI) camera system (light source: double frequency Nd:YAG laser, λ=532 nm) to different types of endoscopes, ex vivo experiments were performed on ten formalin fixed human stomachs, nine containing adenocarcinomas and one with a gastric lymphoma. Linking the endoscopic ESPI camera complex to a fast image processing system, the method of double pulse exposure image subtraction was applied at a video frame rate of 12.5 Hz. Speckle correlation patterns and corresponding phase difference distributions resulting from gastric wall deformation by gentle touch with a guide wire were analyzed. Tumor-free gastric areas showed high-contrast concentric fringes around the point of stimulation. In contrast, fringe patterns and filtered phase difference distributions corresponding to the areas of malignancy in all the cases were characterized by largely parallel lines, indicating that stimulation of rigid tumor tissue primarily led to tilting. Our ex vivo investigations of malignant gastric tumors show that the application of dynamic holographic endoscopy makes it possible to distinguish areas of malignancy from surrounding healthy tissue based on the differences in tissue elasticity.