[OPTICAL REVIEW Vol. 9, No. 6 (2002) 238-243]

Analysis of Spectral Reflectance Using Normalization Method from Endoscopic Spectroscopy System

Masao SAMBONGI, Makoto IGARASHI, Takashi OBI, Masahiro YAMAGUCHI, Nagaaki OHYAMA1 , Masahiko KOBAYASHI2, Yasushi SANO3, Shigeaki YOSHIDA3 and Kazuhiro GONO4

Imaging Science and Engineering Laboratory, Tokyo Institute of Technology, Yokohama 226-8503, Japan
1Frontier Collaborative Research Center, Tokyo Institute of Technology, Yokohama 226-8503, Japan
2Department of Internal Medicine, Self-Defense Force Central Hospital, 1-2-24, Ikejiri, Setagaya, Tokyo, Japan
3Digestive Endoscopy Division National Cancer Hospital East 6-5-1, Kashiwanoda, Kashiwa, Chiba, Japan
4Product Development Department Endoscope Division OLYMPUS OPTICAL Co., Ltd, 2951 Ishikawa-cho Hachioji, Tokyo 192-8507, Japan

(Received January 31, 2002; Accepted September 12, 2002; Revised August 25, 2002)

Objective assessment of gastrointestinal mucosal color is extremely important in the endoscopic diagnosis of digestive tract disease. In this paper, we propose a method to clarify the spectral characteristics of gastric and colon cancer. A large number of spectral reflectance data of mucous membrane are measured by the endoscopic spectroscopy system (ESS) in the National Cancer Center Hospital East, Kashiwa, Japan and the Department of Internal Medicine, Self-Defense Force Center Hospital, Tokyo, Japan. We assume that early cancer appears primarily in the spectral data of short wavelength, because it is usually present in a superficial cell where short wavelength light is scattered more strongly than long wavelength light. To identify the features in the short wavelength components, the spectral reflectance was divided by the reflectance of a long wavelength. We investigated the possibility of distinguishing early cancer from normal spectral data through statistical analysis, employing the projection axis as the mean difference between them. Early cancer and normal spectral data were projected on the projection axis, and the Student's T-test was applied to evaluate the mean of the distribution between these data.

Key words: endoscopic diagnosis, endoscopic spectroscopy system, spectral reflectance, scattering phenomena, statistical analysis