ABSTRACT: We propose a practical and simple measurement function of three dimensional (3D) length for endoscopy based on triangulation
using manually pointed correspondences. This system is a novel combination of conventional methods. 3D length information
is useful for many medical purposes and the burden of manual procedures can be reduced by focusing on length. We employed
a novel combination for length measurement, that is, a monocular endoscope with an electromagnetic tracking sensor. The proposed
method can measure the length without any equipment for light projection and changing the current procedure of endoscopy.
Our method is made more robust and reliable than the automatic correspondence techniques through the best use of the expertise
of endoscopists. We developed a prototype system and evaluated its accuracy. From experimental results, we showed that the
proposed method can measure the 3D length of static objects accurately as long as the measurement geometry is suitable.
Keywordsendoscopy-endoscope-length measurement-manual pointing-electromagnetic tracking sensor-triangulation
Optical Review 04/2012; 17(2):54-60. · 0.66 Impact Factor
ABSTRACT: Many super-resolution methods have been proposed to enhance the spatial resolution of images by using iteration and multiple
input images. In a previous paper, we proposed the example-based super-resolution method to enhance an image through pixel-based
texton substitution to reduce the computational cost. In this method, however, we only considered the enhancement of a texture
image. In this study, we modified this texton substitution method for a hybrid camera to reduce the required bandwidth of
a high-resolution video camera. We applied our algorithm to pairs of high- and low-spatiotemporal-resolution videos, which
were synthesized to simulate a hybrid camera. The result showed that the fine detail of the low-resolution video can be reproduced
compared with bicubic interpolation and the required bandwidth could be reduced to about 1/5 in a video camera. It was also
shown that the peak signal-to-noise ratios (PSNRs) of the images improved by about 6 dB in a trained frame and by 1.0–1.5
dB in a test frame, as determined by comparison with the processed image using bicubic interpolation, and the average PSNRs
were higher than those obtained by the well-known Freeman’s patch-based super-resolution method. Compared with that of the
Freeman’s patch-based super-resolution method, the computational time of our method was reduced to almost 1/10.
Optical Review 04/2012; 17(3):114-122. · 0.66 Impact Factor
ABSTRACT: In this article, we propose an efficient and accurate compressive-sensing-based method for estimating the light transport
characteristics of real-world scenes. Although compressive sensing allows the efficient estimation of a high-dimensional signal
with a sparse or near-to-sparse representation from a small number of samples, the computational cost of the compressive sensing
in estimating the light transport characteristics is relatively high. Moreover, these methods require a relatively smaller
number of images than other techniques although they still need 500–1000 images to estimate an accurate light transport matrix.
Precomputed compressive sensing improves the performance of the compressive sensing by providing an appropriate initial state.
This improvement is achieved in two steps: 1) pseudo-single-pixel projection by multiline projection and 2) regularized orthogonal
matching pursuit (ROMP) with initial signal. With these two steps, we can estimate the light transport characteristics more
accurately, much faster, and with a lesser number of images.
Keywordsimage-based relighting–compressive sensing
Optical Review 04/2012; 18(3):264-272. · 0.66 Impact Factor
ABSTRACT: This paper proposes a practical measurement system for bidirectional reflectance distribution functions (BRDFs) of a three-dimensional
(3D) object with a linear light source. Using the linear light source, the proposed system can reduce the number of image
acquisitions which are necessary for an estimation of the spatially-varying BRDFs of the object. Furthermore, the size of
the proposed system is much smaller than a conventional system which uses a parallel light. In this proposed system, the light
field of the linear light source is previously measured to determine direction and radiance of incident rays to each point
of the object, because the direction and radiance are not constant at each point. Using the proposed system, the BRDF of a
point of flat objects was experimentally measured, and results showed validation of the estimation accuracy of the proposed
system. Measurement efficiency of the proposed system was also evaluated by comparing reflectance model parameters estimated
by the conventional and proposed systems. For the estimation, the reflectance function of a 3D object was measured by both
systems. The estimation accuracy of the proposed method was also evaluated by comparing among a real image and rendered 3D
objects of the conventional and proposed methods.
Optical Review 04/2012; 15(4):187-195. · 0.66 Impact Factor
ABSTRACT: Conventional 3-dimensional color spaces such as L*a*b* or L*C*h have a limitation in that colors of materials can only be separated on the same hyperplane. Therefore, it would be useful to find appropriate axes for dental color analysis by analyzing spectral data itself, rather than conventional 3-dimensional color spaces.
Hyperspectral data are detailed color spectra with narrow spectral bands over a continuous spectral range. We acquired hyperspectral data of the shade guides without specular reflection, and standardized them as reflectance data. Then, reflectance data were weighed by luminous efficiency function, and used in principal component analysis (PCA). Principal components (PCs) and their contribution, and values of respective shades to respective PCs were calculated as PC scores.
Cumulate contribution rate of 1st to 3rd PCs were approximately 100%, which meant shade colors were very similar to each other. Respective PCs showed specific figures, and values of shades showed sequences unique to each PC, which were independent of each other; values to the 1st PC showed gradual changes with change in shade numbering, values to the 2nd PC showed relatively high scores on opaque shades, values to the 4th PC showed lower scores on B and C group shades, and values to the 6th PC showed differences between manufacturers.
Using PCA, we could find axes independent of the conventional 3-dimensional color spaces. These axes reflected certain changes which are not detected on conventional color spaces. Our methods are taking into account color matching under any illumination by focusing on the spectra themselves, and we can discuss about components of the teeth from spectra of resulting principal components. By applying our method to conventional systems, it would help diagnose color differences of dental materials.
Dental materials: official publication of the Academy of Dental Materials 04/2012; 28(7):736-42. · 2.88 Impact Factor
ABSTRACT: In Kampo medicine (Japanese traditional herbal medicine), the appearance of the tongue contains a lot of useful information for diagnosis. However, an inspection of the tongue is not considered to be important in modern medical diagnosis, since the skills applied in the examination are difficult to understand. Thus, we developed an imaging system and algorithm for quantitative analysis of the tongue to provide the traditional techniques of Kampo with greater objectivity.
Tongue images were taken from 9 healthy subjects for 3 consecutive weeks (5 days/week), 12 times a day, with 300 images taken successively within 30 s each time. Then, the temporal color changes in 30 s, 1 day, and 3 weeks were measured in the device-independent International Commission on Illumination (CIE) 1976 L*a*b* color space.
The tongue color change in 30 s varied between individuals, and it was mainly classified into 3 patterns. This image acquisition system and valid color management should help all tongue-related research, and the 30-s temporal color change might be an important target for further tongue analysis.
We were able to acquire tongue images without specular reﬂection and with valid color reproduction, and the color change in 30 s was found to vary. Tongue color changes have not been mentioned in the classics of Kampo medicine, since they were certainly impossible to discriminate by the naked eye. The change during 30 s is a new finding based on the electronic devices, and together they are expected to become a new criterion for tongue analysis.
Forschende Komplementärmedizin / Research in Complementary Medicine 01/2012; 19(2):80-5. · 1.65 Impact Factor
ABSTRACT: Kampo medicine (Japanese traditional herbal medicine) contains concepts useful for preventive medicine. For example, "Mibyou" (disease-oriented state) aims to prevent illness by early recognition. Kampo diagnosis is based on subjective examinations, such as tongue inspection, by trained specialist physicians. An objective metric of the tongue color spectrum was developed as a surrogate for subjective visual inspection.
Tongue images were acquired with a hyperspectral imaging system, and the uncoated tongue region was segmented automatically. The spectral information of the uncoated tongue area was analyzed by principal component analysis (PCA). The component vector most representative of each clinical symptom was found by rotating the vector on a plane spanned by two arbitrary principal component vectors.
The system was tested in human volunteers. Forty-four hyperspectral images were acquired from 30 healthy male subjects for initial testing. The Oketsu (blood stagnation) score was determined by an experienced clinician in Kampo medicine from 27 of 30 subjects. The correlation between respective principal components and Oketsu score was 0.67 at maximum, and increased to 0.73 by linear combination, while it was -0.75 by vector rotation. Significant correlations for many disorders were demonstrated, and vector rotation showed better correlation than linear combination.
A PCA-based algorithm was developed to objectively evaluate patients using color images of the tongue surface. Testing showed that this method was a feasible surrogate for expert visual tongue analysis. This tool should help non-trained people identify "Mibyou" health status for individuals. The algorithm is free of empirical criteria, and it may be it applicable to many hyperspectral image types.
International Journal of Computer Assisted Radiology and Surgery 03/2011; 6(2):209-15. · 1.48 Impact Factor
IEICE Transactions. 01/2011; 94-A:493-499.
IEICE Transactions. 01/2011; 94-D:1768-1777.
Computational Color Imaging - Third International Workshop, CCIW 2011, Milan, Italy, April 20-21, 2011. Proceedings; 01/2011
ABSTRACT: Kampo medicine (Japanese traditional herbal medicine) can identify "Mibyou" (disease-oriented state) based on visual tongue inspection by a trained physician. Surface colors of uncoated tongue provide essential features. A hyperspectral imaging system which performs regional image analysis of the tongue color spectrum was developed to automatically inspect the uncoated tongue.
Hyperspectral tongue surface images were acquired by a camera equipped with an integrating sphere. The color spectrum from 4 tongue areas--uncoated tongue, coated tongue, lip, and perioral areas--were quantified. The average spectrum of each area was determined and 4 images calculated by focusing on the differences between respective spectra; highlight, shadow, tongue coat, and lip-weighted images were calculated. The uncoated tongue area was extracted by subtraction.
Reproducibility was evaluated by applying the camera and extraction algorithm to 44 images from human subjects. Eighty-two percentage were judged as acceptable by a Kampo medicine physician expert.
Using a hyperspectral camera and extraction algorithm, the tongue color of the uncoated part was automatically extracted. This technique is suitable for tongue color analysis and may help non-trained users to identify "Mibyou".
International Journal of Computer Assisted Radiology and Surgery 01/2011; 6(1):143-52. · 1.48 Impact Factor
IEICE Transactions. 01/2010; 93-D:882-890.
IEICE Transactions. 01/2010; 93-D:1253-1262.
ICAART 2010 - Proceedings of the International Conference on Agents and Artificial Intelligence, Volume 1 - Artificial Intelligence, Valencia, Spain, January 22-24, 2010; 01/2010
Computer Vision - ACCV 2010 Workshops - ACCV 2010 International Workshops, Queenstown, New Zealand, November 8-9, 2010, Revised Selected Papers, Part I; 01/2010
IEICE Transactions. 01/2010; 93-D:1878-1888.
ABSTRACT: In this article, we propose an effective colorprocessing algorithm to analyze the hyperspectral image of the tongue and its application to preventive medicine by the concept of Japanese traditional herbal medicine (Kampo medicine). Kampo medicine contains a number of concepts useful for preventive medicine such as "Mibyou" - disease-oriented state - signs of abnormalities. Hyperspectral images of the tongue were taken with the system with an integrating sphere, and tongue area without coating was eliminated automatically. Then, spectral information of the tongue area without coating was analyzed by principal component analysis, and the component vector best representing the clinical symptom was found by rotating the vector on a plane spanned by two arbitrary principal component vectors.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2010; 2010:3025-8.
IEICE Transactions. 01/2009; 92-D:310-318.
J. Electronic Imaging. 01/2009; 18:043008.
International Conference on Computer Graphics and Interactive Techniques, SIGGRAPH ASIA 2009, Yokohama, Japan, December 16-19, 2009, Poster Proceedings; 01/2009