Kazuhiro Gono

Appearance of enhanced tissue features in narrow-band endoscopic imaging

This study was performed to examine the usefulness of medical endoscopic imaging utilizing narrow-band illumination. The contrast between the vascular pattern and the adjacent mucosa of the underside of the human tongue was measured using five narrow-band illuminations and three broadband illuminations. The results demonstrate that the pathological features of a vascular pattern are dependent on the center wavelength and the bandwidth of illumination. By utilizing narrow-band illumination of 415+/-30 nm, the contrast of the capillary pattern in the superficial layer was markedly improved. This is an important benefit that is difficult to obtain with ordinary broadband illumination. The appearances of capillary patterns on color images were evaluated for three sets of filters. The narrow, band imaging (NBI) filter set (415+/-30 nm, 445+/-30 nm, 500+/-30 nm) was selected to achieve the preferred appearance of the vascular patterns for clinical tests. The results of clinical tests in colonoscopy and esophagoscopy indicated that NBI will be useful as a supporting method for observation of the endoscopic findings of early cancer.

Multiple-discriminant analysis for light-scattering spectroscopy and imaging of two-layered tissue phantoms

We propose a new method for enhancing the sensitivity of the reflectance spectrum to the scattering feature of the superficial tissue layer. This method is based on multiple-discriminant analysis in the eigensubspace of the spectrum. Considering the application of scattering imaging, we evaluated this method by performing multispectral imaging of two-layered tissue phantoms. A color map converted from the spectral reflectance corresponds well to variations in the size of the scattering in the first layer.

Analysis of spectral reflectance of mucous membrane for endoscopic diagnosis

Using color of mucous membrane is extremely important in endoscopic diagnosis. We have developed an endoscopic spectroscopy system (ESS) to clarify spectral characteristics of gastric and colon cancer, and a large amount of spectral reflectance data of mucous membrane has been measured by ESS. This paper proposes a method to find the spectral features of lesions considering the light scattering phenomena. We suppose that the influence of mucous membrane, i.e., tumor mainly appear in the spectral data of short wavelength, because the tumor of early cancer is usually present in superficial cell where short wavelength light is scattered more strongly than long wavelength light. To reveal the features in the short wavelength components, the spectral reflectance is divided by the same reflectance of a certain long wavelength. Then, the effect of individual variation on the mucosal color is reduced by subtracting the reflectance of normal region from that of adjacent tumor region. We apply principal component analysis and statistical discriminant analysis to the subtracted spectral reflectance data; the difference between the tumor and normal tissue is revealed.

Novel endoscopic imaging system for early cancer diagnosis

We have developed the novel video endoscope imaging techniques; Narrow band imaging (NBI), Auto-Fluorescence Imaging (AFI), Infra-Red Imaging (IRI) and Endo-Cytoscopy System (ECS). The purpose of these imaging techniques is to emphasize the important tissue features associated with early stage of lesions. We have already launched the new medical endoscope system including NBI, AFI and IRI (EVIS LUCERA SPECTRUM, OLYMPUS MEDICAL SYSTEMS Co., Ltd., Fig.1). Moreover ECS, which has enough magnification to observe cell nuclei on a superficial mucosa under methylene blue dye staining, is the endoscopic instrument with ultra-high optical zoom. In this paper we demonstrate the concepts and the medical efficacy of each technology.

Simulation of spectral reflectance of multiple scattering medium using the Mie theory combined with the Monte Carlo method

We present the method which can calculate the spectral reflectance from physical parameters corresponding to the pathological features, e.g. average size of cell nuclei and standard deviation of cell nuclear size distribution, in consideration of multiple scattering in biological tissue. In this paper, the method combined the Monte Carlo method which simulates multiple scattering effects and the Mie theory which provides phase function (angular properties of light scattering) and scattering coefficient was employed. In order to investigate the validity of this method, the calculated spectra by the method and Monte Carlo method with Henyey-Greenstein phase functions were compared with measurement spectra derived from the tissue phantom whose size distribution has double peaks. From the results, it is shown that the method can better predict the spectral reflectance of tissue phantom rather than Monte Carlo method with Henyey-Greenstein phase function.

Recent development in multifunctional endoscope

We have developed the novel video endoscope imaging techniques; Narrow band imaging (NBI), Auto-Fluorescence Imaging (AFI), Infra-Red Imaging (IRI) and Endo-Cytoscopy System (ECS). The purpose of these imaging techniques is to emphasize the important tissue features associated with early stage of lesions. We have already launched the new medical endoscope system including NBI, AFI and IRI (EVIS LUCERA SPECTRUM, OLYMPUS MEDICAL SYSTEMS Co., Ltd., Fig.1). Moreover ECS, which has enough magnification to observe cell nuclei on a superficial mucosa under methylene blue dye staining, is the endoscopic instrument with ultra-high optical zoom. In this paper we demonstrate the concepts and the medical efficacy of each technology.