Dynamic fluorescence video endoscopy for intravital evaluation of gastrointestinal mucosal blood flow

Raman endoscopy for in vivo differentiation between benign and malignant ulcers in the stomach

The aim of this study was to evaluate the clinical utility of an image-guided Raman endoscopy technique for in vivo differential diagnosis of benign and malignant ulcerous lesions in the stomach. A rapid-acquisition image-guided Raman endoscopy system with 785 nm laser excitation has been developed to acquire in vivo gastric tissue Raman spectra within 0.5 s during clinical gastroscopic examinations. A total of 1102 in vivo Raman spectra were acquired from 71 gastric patients, in which 924 Raman spectra were from normal tissue, 111 Raman spectra were from benign ulcers whereas 67 Raman spectra were from ulcerated adenocarcinoma. There were distinctive spectral differences in Raman spectra among normal mucosa, benign ulcers and malignant ulcers, particularly in the spectral ranges of 800-900, 1000-1100, 1245-1335, 1440-1450 and 1500-1800 cm(-1), which primarily contain signals related to proteins, DNA, lipids and blood. The malignant ulcerous lesions showed Raman signals to be mainly associated with abnormal nuclear activity and decrease in lipids as compared to benign ulcers. Partial least squares-discriminant analysis (PLS-DA) was employed to generate multi-class diagnostic algorithms for classification of Raman spectra of different gastric tissue types. The PLS-DA algorithms together with leave-one tissue site-out, cross validation technique yielded diagnostic sensitivities of 90.8%, 84.7%, 82.1%, and specificities of 93.8%, 94.5%, 95.3%, respectively, for classification of normal mucosa, benign and malignant ulcerous lesions in the stomach. This work demonstrates that image-guided Raman endoscopy technique associated with PLS-DA diagnostic algorithms has for the first time promising clinical potential for rapid, in vivo diagnosis and detection of malignant ulcerous gastric lesions at the molecular level.

Detection of the fluorescence of GI vessels in rats using a CCD camera or a near-infrared video endoscope

BACKGROUND

Choroidal near-infrared fluorescent angiography can detect vessels in the eye with high resolution. Observation of fluorescent gastrointestinal (GI) vessels by endoscopy may be useful in portal hypertension and bleeding ulcer. We here describe a technique for the detection of fluorescent GI vessels with a CCD camera or a near-infrared video endoscope.

METHODS

Laparotomy was performed on rats. A tissue target was excited by means of a laser diode. We took pictures of tissue under both white and near-infrared light, both before and after intravenous injection of indocyanine green. Fluorescent light was selected by means of filters placed in front of the lens of a CCD camera or a near-infrared video endoscope.

RESULTS

Under near-infrared light and after dye injection, we observed fluorescent vessels in real time and distinguished arterial from venous fluorescence.

CONCLUSIONS

This device permits visualization of GI vessels, which could be useful for diagnosis of vascular abnormalities during endoscopy and surgery.

Mathematical model of fluorescence endoscopic image formation

We present a mathematical model that describes the spatial distribution of photons in fluorescence endoscopic images, resulting in expressions for image signal-to-noise ratio and resolution. This model was applied to quantitative analysis of fluorescence images collected from human colonic mucosa with a fiber-optic and an electronic endoscope. It provides a tool for the design of fluorescence endoscopic imaging systems and for extraction of quantitative information about image features. The results apply generally to endoscopic imaging of remote structures in biological and industrial settings, in which light of weak intensity such as fluorescence as well as reflected white light is used.

A method for the estimation of the hemoglobin distribution in gastroscopic images

The assessment of blood flow in the gastrointestinal mucosa could be a useful indicator for the diagnosis and treatment of several diseases, such as ulcers, gastritis, colitis or early cancer. The quantity of blood flow is roughly estimated by computing the spatial hemoglobin distribution in the mucosa. The method presented here enables a practical realization by calculating approximately the hemoglobin concentration based on a spectrophotometric analysis of endoscopic true-color images, which are recorded during routine examinations. A system model based on the reflectance spectroscopic law of Kubelka-Munk is derived, which enables an estimation of the hemoglobin concentration by means of the color values of the images. Additionally, a transformation of the color values is developed, in order to improve the luminance independence. Applying this transformation and estimating the hemoglobin concentration for each pixel of interest, the hemoglobin distribution can be computed. The results obtained are mostly independent of luminance. An initial validation of the method is made by a quantitative estimation of the reproducibility.

Future developments in endoscopic imaging

Endoscopic imaging capabilities have significantly improved over the past 10 years. Improvements in fibreoptic technology have made possible the development of very thin endoscopes that can directly visualize the biliary and pancreatic ducts. The application of the CCD to endoscopy has made electronic endoscopy possible, and holds promise for stereoendoscopy. The ability to digitize endoscopic images can be developed to store, transmit, magnify, enhance and otherwise manipulate data obtained during endoscopy, and will probably be utilized routinely in the future. Laser and ultrasound technology are likely to enhance significantly our ability to examine ultrastructural aspects of gastrointestinal organs and surrounding tissues, and may play an important role in cancer surveillance programs. Vital staining techniques are likely to find widespread use in early cancer detection programmes, and may be useful to follow prospectively lesions observed or treated during endoscopy. Finally, the new developments in 'virtual imaging' may find applications in the field of gastrointestinal endoscopy and other 'minimally invasive' surgical procedures.