Showing papers by "Nagaaki Ohyama published in 2004"
TL;DR: 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.
Abstract: 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 demon- strate that the pathological features of a vascular pattern are depen- dent on the center wavelength and the bandwidth of illumination. By utilizing narrow-band illumination of 415630 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 broad- band illumination. The appearances of capillary patterns on color im- ages were evaluated for three sets of filters. The narrow, band imaging (NBI) filter set (415630 nm, 445630 nm, 500630 nm) was selected to achieve the preferred appearance of the vascular patterns for clini- cal tests. The results of clinical tests in colonoscopy and esophagos- copy indicated that NBI will be useful as a supporting method for observation of the endoscopic findings of early cancer. © 2004 Society of
858 citations
Journal Article•
TL;DR: In this article, a six-band high-definition television (HDTV) camera system was proposed for accurate color reproduction of motion pictures based on spectral information, which has an optical component connecting the objective lens to two conventional HDTV camera heads whose spectral sensitivities are individually adjusted by placing different interference filters between the objective and each camera.
Abstract: We present the architecture of a six band high-definition television (HDTV) camera system newly developed for accurate color reproduction of motion pictures based on spectral information. The camera has an optical component connecting the objective lens to two conventional HDTV camera heads whose spectral sensitivities are individually adjusted by placing different interference filters between the objective lens and each camera. Evaluation of the accuracy of the color estimation obtained using the six band camera and a conventional RGB, i.e., three band, HDTV camera using simulated and experimentally obtained camera signals showed that the six band camera achieves accurate color estimation. In the experimental evaluation, the average color differences for the 24 color patches of the GretagMacbeth Color Checker for the six band and RGB camera signals were 1.43 and 4.12 delta-E a b . This system should thus be suitable for a wide variety of applications.
61 citations
TL;DR: A new color conversion method for multi-primary display that reduces the observer metamerism is proposed and gives the multi-dimensional control value of a display device to minimize the spectral approximation error under the constraints of tristimulus match.
Abstract: In the conventional color reproduction based on the colorimetric match for a standard observer, color mismatch can be perceived if the color matching functions of the observer deviate from those of the standard observer; this phenomenon is known as observer metamerism. Recently, multi-primary display, using more than three-primary colors, has attracted attention as a color reproduction media because of its expanded gamut and its possibility to reduce the color mismatch caused by observer metamerism. In this paper, a new color conversion method for multi-primary display that reduces the observer metamerism is proposed. The proposed method gives the multi-dimensional control value of a display device to minimize the spectral approximation error under the constraints of tristimulus match. Reproduced spectrum by a seven-primary display is simulated and evaluated by the color matching functions of Stiles's 20 observers. The results confirmed that the proposed method reduces the color reproduction error caused by observer variability compared to the other seven-primary reproduction and conventional three-primary reproduction. The preliminary visual evaluation results with a seven-primary display using light-emitting diodes are also introduced.
24 citations
TL;DR: A comparison of four spectral transforms presented before to find out which transform is more suitable to a spectral decorrelation scheme in transform coding of multispectral images finds that WKLT and OMA reduced colorimetric error compared to the others.
Abstract: Recently, multispectral images have been utilized for high fidelity color reproduction through visual telecommunication systems and its compression schemes have been required. However multispectral image coding considering color degradation has not been established. This article presents a comparison of four spectral transforms presented before to find out which transform is more suitable to a spectral decorrelation scheme in transform coding of multispectral images. Transforms dealt with in this paper are Karhunen-Loeve transform (KLT), weighted KLT (WKLT), one mode analysis (OMA) and a transform realizing compatibility to the conventional color systems, latter three of which are designed to represent spectral reflectance functions with small number of coefficients having small colorimetric errors. Through the theoretical and experimental comparisons, it is found that WKLT and OMA reduced colorimetric error compared to the others, where OMA is suitable when the rendering illuminations in the color reproduction can be assumed in advance and WKLT is applicable to other situations.
24 citations
TL;DR: A new method is proposed based on multiple-discriminant analysis in the eigensubspace of the spectrum for enhancing the sensitivity of the reflectance spectrum to the scattering feature of the superficial tissue layer by performing multispectral imaging of two-layered tissue phantoms.
Abstract: 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.
15 citations
Journal Article•
TL;DR: The collection of original MEXICAN CODIICES as mentioned in this paper is one of the most important collections in the world and it is under the CUSTODY of the NATIONAL LIBRARY OF ANTHROPOLOGY and HISTORY.
Abstract: LOS CODICES MEXICANOS SON UN ANTIGUO SISTEMA DE LECTURA Y ESCRITURA DESARROLLADO POR LAS CULTURAS PRE-HISPANICAS DE MESOAMERICA. ESTOS DOCUMENTOS PICTORICOS SON UN LEGADO CULTURAL, PARTE DEL CUAL DATA DEL SIGLO XVI. LA COLECCION CONOCIDA COMO ”COLECCION DE CODICES MEXICANOS ORIGINALES” ES UNA DE LAS MAS IMPORTANTES COLECCIONES ALREDEDOR DEL MUNDO Y SE ENCUENTRA BAJO LA CUSTODIA DE LA BIBLIOTECA NACIONAL DE ANTROPOLOGIA E HISTORIA (BNAH) EN LA CIUDAD DE MEXICO. PARA LA PRESERVACION DE LOS DOCUMENTOS, LA COLECCION SE ENCUENTRA BAJO ACCESO LIMITADO Y LAS CONDICIONES PARA SU ILUMINACION SE MANTIENEN CONTROLADAS, UNICAMENTE SE PERMITEN LAMPARAS DE TUNGSTENO PARA ILUMINACION DE LOS CODICES Y LA INTENSIDAD NO DEBE EXCEDER DE 1000 LUXES. PARA LLEVAR A CABO UNA REPRODUCCION EXACTA DE LOS COLORES DE LOS CODICES ORIGINALES, HEMOS PROPUESTO A LA BNAH UN ENFOQUE MULTIESPECTRAL. NUESTRO METODO PARA LA REPRODUCCION DEL COLOR ESTA BASADO EN LA ESTIMACION DE LA REFLECTANCIA ESPECTRAL EN CADA UNO DE LOS PIXELES EN LA IMAGEN A PARTIR DE UN CONJUNTO DE IMAGENES MULTIESPECTRALES DE 16 BANDAS. EL ENFOQUE MULTIESPECTRAL NOS PERMITE REMOVER LA ILUMINACION ORIGINAL DE TUNGSTENO USADO EN LA CAPTURA, Y REALIZAR UNA SIMULACION DE COLOR BAJO CUALQUIER ILUMINACION ARBITRARIA, POR EJEMPLO, CIE-D65, POR LO TANTO ESTE ENFOQUE NOS PERMITE REPRODUCIR LOS COLORES NATURALES (TRUE COLORS) DE LOS CODICES ORIGINALES. EN ESTE ARTICULO PRESENTAMOS LOS RESULTADOS DE DIVERSAS APROXIMACIONES PARA LA ESTIMACION DEL ESPECTRO BAJO LAS CONDICIONES DE ILUMINACION ESTABLECIDAS POR LA BNAH Y MOSTRAMOS LA SIMULACION DE COLOR DE UNA REPLICA DE CODICE BAJO CIE-D65. Abstract MEXICAN CODICES ARE AN ANCIENT READING AND WRITING SYSTEM DEVELOPED BY THE PRE-HISPANIC CULTURES OF MESOAMERICA. THESE PICTORIAL DOCUMENTS ARE A CULTURAL LEGACY, PART OF WHICH DATES FROM THE 16TH CENTURY. THE COLLECTION KNOWN AS ”COLLECTION OF ORIGINAL MEXICAN CODICES” IS ONE OF THE MOST IMPORTANT CODICES COLLECTION AROUND THE WORLD AND IT IS UNDER THE CUSTODY OF THE NATIONAL LIBRARY OF ANTHROPOLOGY AND HISTORY (BNAH, BIBLIOTECA NACIONAL DE ANTROPOLOGIA E HISTORIA) IN MEXICO CITY. FOR PRESERVATION OF THE DOCUMENTS, THE COLLECTION IS KEPT UNDER LIMITED ACCESS AND CONTROLLED ILLUMINATION CONDITIONS, ONLY TUNGSTEN LAMPS ARE ALLOWED FOR ILLUMINATION OF CODICES AND LIGHT INTENSITY SHOULD NO EXCEED 1000 LUX. IN ORDER TO ACHIEVE ACCURATE COLOR REPROD
15 citations
TL;DR: A comparative evaluation is performed on the smoothness of the gradation patterns among three color conversion algorithms and it was confirmed that a method that generates smooth signal all over the color gamut gave the smoothest gradation both objectively and subjectively.
Abstract: Multi-primary displays, which enable to expand their color gamut, have a degree of freedom in the selection of the device control signals to reproduce a set of tristimulus values. To reproduce a given tristimulus values on a multi-primary display, we need a color conversion algorithm which gives a unique set of device control signals; several algorithms with different characteristics have been proposed. However, they do not guarantee that control signals change smoothly even when tristimulus values change smoothly. Such signal discontinuity is pointed out as a cause of pseudo contour appeared in smooth tonal change when color matching functions of observers are deviated from the standard one or when device profiles include some error. In this article, first, the relation between signal discontinuity and pseudo contour is theoretically analyzed. Then a comparative evaluation is performed on the smoothness of the gradation patterns among three color conversion algorithms. As a result of the comparison, it was confirmed that a method that generates smooth signal all over the color gamut gave the smoothest gradation both objectively and subjectively.
13 citations
01 Jan 2004
TL;DR: Through the experiments using the H&E stained slides of liver tissue, the color was almost successfully corrected by the proposed color correction method.
Abstract: The color of hematoxylin & eosin (H&E) stained tissue image varies with the staining conditions and with the characteristics of the microscope and imaging devices. This color variation affects the diagnostic examination. This paper proposes a color correction method for images of pathological slides prepared under inappropriate staining-condition. In the proposed method, the spectral transmittance obtained by a multispectral digital camera is utilized to estimate the amount of dye for each pixel. Subsequently the amount of dye is adjusted based on the chemical kinetic equation by digital process, so that the dye amount distribution would be equivalent to that of the reference slide, which is prepared under ideal staining conditions. Through the experiments using the H&E stained slides of liver tissue, the color was almost successfully corrected by the proposed method.
12 citations
Proceedings Article•
01 Jan 2004
9 citations
TL;DR: In this article, the spectral transmittance obtained by a multispectral digital camera is utilized to estimate the amount of dye for each pixel, and then the amount was adjusted based on the chemical kinetic equation by digital process, so that the dye amount distribution would be equivalent to that of the reference slide.
Abstract: The color of hematoxylin & eosin (H&E) stained tissue image varies with the staining conditions and with the characteristics of the microscope and imaging devices. This color variation affects the diagnostic examination. This paper proposes a color correction method for images of pathological slides prepared under inappropriate staining-condition. In the proposed method, the spectral transmittance obtained by a multispectral digital camera is utilized to estimate the amount of dye for each pixel. Subsequently the amount of dye is adjusted based on the chemical kinetic equation by digital process, so that the dye amount distribution would be equivalent to that of the reference slide, which is prepared under ideal staining conditions. Through the experiments using the H&E stained slides of liver tissue, the color was almost successfully corrected by the proposed method.
7 citations
Journal Article•
TL;DR: In this paper, a virtual multispectral camera (VMSC) is proposed to transform real multi-spectral images into virtual multi-spectral images, which can avoid the large differences in dynamic range between coefficients of the basis functions derived from the PCA and negative pixel values.
Abstract: We propose a simple but useful method to represent multispectral images captured by multispectral cameras (MSC) with different numbers of bands. When considering accurate color reproduction under an arbitrary illuminant, it is necessary to represent them in a common space with sufficient accuracy of spectral information, estimated from each multispectral image. The principal component analysis (PCA) is useful to reduce the high dimension of the spectral information. However, PCA-based methods may cause both large differences in dynamic range between coefficients of the basis functions derived from the PCA and negative pixel values, therefore, it is not easy to handle or edit coefficient images. To solve the problem, we propose the idea of a virtual multispectral camera (VMSC) that transforms real multispectral images into virtual multispectral images. We design the sensitivities of the VMSC properly, and our unified representation can avoid some disadvantages of conventional PCA-based methods. We experimentally demonstrate the color reproduction accuracy of our method by comparing it with the PCA-based methods, and we show an example of a virtual multispectral image transformed by our method.
Journal Article•
TL;DR: In this paper, a linear combination of the multispectral images as interpolation function is proposed, which is equivalent to fitting the data to a straight line in a 16-dimentional space.
Abstract: We present a proposal to achieve accurate color reproduction by fitting the CIE-XYZ tristimulus values of a given color stimulus, and using the 16-band multispectral images, as well as the CIE-XYZ tristimulus values of a known color test chart. We propose a simple linear combination of the multispectral images as interpolation function, which is equivalent to fitting the data to a straight line in a 16-dimentional space. By using this interpolation function, we minimize the merit function of the mean error between the measured and estimated CIEXYZ tristimulus values of the color test chart. We show, by making a visual comparison between the results achieved using this proposal and the results achieved using a spectral reflectance estimation technique, that the proposed interpolation function when using 16-channel multispectral images produces high quality results in terms of color reproduction fidelity.
Proceedings Article•
01 Jan 2004
08 Aug 2004
TL;DR: "Natural Vision" is a novel color imaging technology developed through research into high-fidelity image reproduction for TV systems, i.e., high fidelity in terms of color, glosses and textures.
Abstract: "Natural Vision" is a novel color imaging technology developed through research into high-fidelity image reproduction for TV systems, i.e., high fidelity in terms of color, glosses and textures. The technology has been studied since 1999 in a research project directly controlled by the Telecommunications Advancement Organization of Japan (The present National Institute of Information and Communication Technology).
07 Jan 2004
TL;DR: Through the experiments using some 16-band multispectral images, it is confirmed that the proposed method reduces the average and the maximum color differences in L*a*b* color space in comparison with the conventional methods.
Abstract: Color reproduction systems using multispectral imaging techniques make it possible to accurately reproduce the color of the original object under various viewing illuminants. In this paper, a multispectral image compression method for high fidelity color reproduction is proposed in consideration of color degradation. In the proposed method, a spectral transform and a nonlinear quantization designed to reduce colorimetric error are combined with the discrete wavelet transform in JPEG2000. Through the experiments using some 16-band multispectral images, it is confirmed that the
proposed method reduces the average and the maximum color differences in L*a*b* color space in comparison with the conventional methods.
TL;DR: In this article, a tissue phantom with double-peak particle size distribution was made and measured using a single optical fiber, and compared the measured spectra with the calculated ones using the Monte Carlo (MC) method, showing that the Mie phase function characterizes better than the Henyey-Greenstein (H-G) phase function.
Abstract: We made a tissue phantom with double-peak particle size distribution, which has polystyrene particles of cell nuclear size and mitochondrial size, and measured the spectrum from the tissue phantom using a single optical fiber. In this paper we investigate the characterization method for the tissue phantom with double-peak particle size distribution by comparing the measured spectra with the calculated ones using the Monte Carlo (MC) method. It is first shown that the Mie phase function characterizes better than the Henyey-Greenstein (H-G) phase function in MC calculation. Next, we compare the measurement spectra with those obtained by modeling as single-peak, conventional modeling for particle size distribution, and for double-peak particle size distribution. The single-peak modeling is found to cause considerable error for the tissue phantom with double-peak particle size distribution, which seems to simulate a biological tissue. We suggest that if one simulates the particle size distribution of a biological tissue by conventional modeling, the accuracy of estimation will be lower.
16 Oct 2004
TL;DR: Experimental results show that the proposed histogramming method keeping the advantage of DOI information, and the image quality of the JPET-D4 is superior to a conventional NonDOI PET scanner.
Abstract: The next generation PET scanner named JPET-D4 has been developed at the National Institute of Radiological Sciences (NIRS) in Japan The JPET-D4 has 4 layers DOI detectors and its data size becomes huge to handling Then at first stage, we plan to apply the reconstruction techniques after the histogramming of list-mode data because it is easy to implement and effective to decrease computational cost The conventional histogramming technique is inapplicable to 4 layers DOI detectors, so we proposed the new histogramming method which is suitable for the multi-layer DOI detector In this method, DOI-PET list-mode data is transformed into sinogram with an accurate system model of the crystal block In this paper, we implemented this method with a full three dimensional system model And we also applied the method to experimental data with prototype system for the JPET-D4 scanner Experimental results show that the proposed method keeping the advantage of DOI information, and the image quality of the JPET-D4 is superior to a conventional NonDOI PET scanner
Proceedings Article•
01 Jan 2004
TL;DR: In this paper, the authors proposed a method to enhance the sensitivity of the reflectance spectrum to the scattering feature of the superficial tissue layer by using multiple discriminant analysis in the eigen subspace of the spectrum.
Abstract: Here, we propose a new method to enhance the sensitivity of the reflectance spectrum to the scattering feature of the superficial tissue layer. This method is based on multiple discriminant analysis (MDA) in the eigen subspace 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 well corresponds to variations in the size of the scatter in the first layer. In order to confirm our proposed method works well under more realistic conditions, we performed the computational simulations of the light propagation in the tissue. We used the simulation model combined with the Monte Carlo and the Mie scattering. Its conditions like the slab geometry and the particle distribution of the cell nucleus were estimated by the image measuring of pathological slices. Results on simulations show the possibility of enhancing the sensitivity of the reflectance spectrum to the scattering feature of the superficial tissue layer.