Endoscopic fluorescence spectroscopic imaging in the gastrointestinal tract.

Fluorescence detection is one of a series of new optical biopsy techniques that have been adapted and evaluated for implementation in gastrointestinal endoscopy. Endogenous fluorescence enables the detection of metabolic and structural changes in human tissue and thus may offer information for the detection of early stage dysplastic and malignant lesions of the mucosa that remain invisible in white light endoscopy. Tissue fluorescence can be detected by point-spectroscopic sampling of the mucosa or by processing the fluorescence information to generate an endoscopic image. Different approaches have been evaluated in pilot studies, and the results in terms of high diagnostic sensitivity and specificity are encouraging. However, large multi-center trials are necessary to evaluate the accuracy and predictability of these new optical tools for the endoscopic diagnosis of early cancerous lesions in the gastrointestinal tract.

Endoscopic light-induced autofluorescence spectroscopy for the diagnosis of colorectal cancer and adenoma.

To evaluate the new, bio-optical method of light-induced autofluorescence spectroscopy for the endoscopic in-vivo diagnosis of (pre)-cancerous lesions of the colorectum, 311 endogenous fluorescence spectra were obtained from normal, adenomatous and cancerous colorectal tissue in 11 patients with cancer, six patients with familial adenomatous polyposis, and six patients with multiple adenomatous polyps. A light source delivered either white or violet-blue light for excitation of tissue autofluorescence via a flexible endoscope. Endogenous fluorescence spectra emitted by the tissue were picked up with a fiberoptic probe and analysed with a spectrograph. Biopsies were taken for definitive classification of the spectra. Rectal cancer (n=11) as well as adenomas with severe dysplasia (n=19) showed specific differences between the emitted fluorescence spectra as compared with normal mucosa and hyperplastic polyps. Having applied a mathematical algorithm to the spectra, a sensitivity of 96% and a specificity of 93% were obtained for the diagnosis of rectal cancer. The equivalent values for the diagnosis of dysplastic ademomas were 98 and 89%, respectively. Light-induced autofluorescence spectroscopy is a new and promising bio-optical procedure for the endoscopic in-vivo diagnosis of colorectal cancer and dysplasia.

Evaluation of sensitivity and inter- and intra-observer variability in the detection of intestinal metaplasia and dysplasia in Barrett's esophagus with enhanced magnification endoscopy.

OBJECTIVE: Magnification endoscopy with acetic acid or dye for diagnosis of Barrett's esophagus is presently undergoing clinical evaluation. Current studies report good accuracy in predicting specialized intestinal metaplasia. To date, however, there is no definitive information on the inter- and intra-observer variability of these methods applied to the diagnosis of normal and dysplastic Barrett's mucosa. MATERIAL AND METHODS: Sixty patients with endoscopically suspected Barrett's esophagus were investigated prospectively with the zoom endoscope after contrast enhancement of the mucosa with 1.5% acetic acid. Two hundred and twenty-three enlarged and histologically investigated areas of gastric, cardiac, normal and dysplastic Barrett's mucosa were photodocumented and in randomized sequence presented to 4 endoscopists in a blinded manner (2 with and 2 without experience of zoom endoscopy for evaluation). The reference for the first evaluation (A1) was standard endoscopic photographs of the respective, histologically confirmed mucosal entity. In a second evaluation (A2), the pictures were again interpreted by the same blinded investigators, but this time a modified pit-pattern classification as proposed by Sharma et al. was employed as the evaluation reference. RESULTS: The diagnostic sensitivity for specialized intestinal metaplasia and dysplasia in Barrett's esophagus calculated for the A1 evaluation ranged -- investigator dependently -- from 54.9% to 80.7% and for A2 from 42.2% to 81.5%. The inter- and intra-observer variability for the evaluation procedure A1 and A2 was high (all kappa values <0.4). In particular, the inexperienced investigators demonstrated high intra-observer variability and low sensitivity in comparison with the experienced investigators. CONCLUSIONS: The diagnosis of Barrett's mucosa using enhanced magnification endoscopy after acetic acid instillation is associated with a high level of interobserver variability. One reason is a frequent mismatch between cardiac mucosa and non-dysplastic Barrett's mucosa.

Evaluation of in vivo endoscopic autofluorescence spectroscopy in gastric cancer.

BACKGROUND: The aim of this study was to evaluate light-induced autofluorescence spectroscopy for the in vivo diagnosis of gastric cancer. METHODS: A total of 344 endogenous fluorescence spectra were obtained from normal (164) and cancerous gastric mucosa (180) in 15 patients with pure adenocarcinoma and in 16 patients with gastric cancer containing signet-ring cells. A special light source capable of delivering either white or violet-blue light for the excitation of tissue autofluorescence via the endoscope was used. Endogenous fluorescence spectra emitted by the tissue were collected with a fiberoptic probe and analyzed with a spectrograph. RESULTS: Gastric adenocarcinoma exhibits specific changes in the emitted fluorescence spectra as compared with normal gastric mucosa. By algorithmic classification of the spectra, a sensitivity of 84%, specificity of 87%, a likelihood ratio for a positive test of 6.5 and for a negative test of 0.18 were obtained for the diagnosis of pure adenocarcinoma of the stomach. However, gastric cancer with signet-ring cells exhibits great variation in emitted autofluorescence spectra as compared with normal mucosa. The sensitivity for the diagnosis of all carcinomas containing signet-ring cells was 55%, specificity 85%, the likelihood ratio for a positive test was 3.7 and for a negative test, 0.53. The diagnostic value decreases with increasing numbers of signet-ring cells and tumor grade. CONCLUSIONS: Light-induced autofluorescence spectroscopy is a new and promising bio-optical technique for the endoscopic in vivo diagnosis of gastric adenocarcinoma. The poor diagnostic accuracy for signet-ring cell carcinoma may be explained by the diffuse and frequent submucosal growth of this tumor and the presence of collagen fibers.