Nagaaki Ohyama

Bio: Nagaaki Ohyama is an academic researcher from Tokyo Institute of Technology. The author has contributed to research in topics: Color image & Image processing. The author has an hindex of 32, co-authored 258 publications receiving 4480 citations. Previous affiliations of Nagaaki Ohyama include National Institute of Information and Communications Technology.

Three-dimensional image reconstruction for JPET-D4 using suitable histogramming method to DOI detector

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

Shape Measurement from Endoscopic Images : Determination of Dimensional Scale Factor by a Photometric Method

Abstract: We propose a new method to measure surface topography using a monocular endoscope. The surface structure is obtained up to a scale factor from an image sequence taken through a conventional CCD endoscope. The scale factor is determined by a photometric method, and the actual size of the object can be determined. The principle and experimental results are presented.

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

Abstract: 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.

Fast estimation of scatter components with good accuracy by using OS-EM techniques for scatter subtraction

Abstract: In this work, we propose a method for scatter compensation in SPECT imaging, by which we can estimate the scatter components in projections in high speed with a good accuracy. The method is that, at first, we estimate the scatter components in projections based on scatter response kernels by one time of OS-EM iteration, and then, subtract the estimated scatter components from the projections and complete the reconstruction by FBP method. The principle is that, the image corresponding to the scatter components in projections consist of almost low-frequency components of the activity distribution and the low-frequency components will converge faster than the high ones during iterative reconstruction. Therefore, we can estimate the low-frequency component image before the image converges with high-frequency ones and estimate the scatter components by re-projecting the low- frequency component image with scatter response kernels. The effects of the method were compared with dual- and triple- energy window methods using experimental measurements. The results show a good accuracy in estimated scatter components, a good uniformity of subtraction at both the center and side spheres and a good noise property can be acquired by proposed method compared with the dual- and triple-energy window methods.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Intelligent electronic appliance system and method

Abstract: An intelligent electronic appliance preferably includes a user interface, data input and/or output port, and an intelligent processor. A preferred embodiment comprises a set top box for interacting with broadband media streams, with an adaptive user interface, content-based media processing and/or media metadata processing, and telecommunications integration. An adaptive user interface models the user, by observation, feedback, and/or explicit input, and presents a user interface and/or executes functions based on the user model. A content-based media processing system analyzes media content, for example audio and video, to understand the content, for example to generate content-descriptive metadata. A media metadata processing system operates on locally or remotely generated metadata to process the media in accordance with the metadata, which may be, for example, an electronic program guide, MPEG 7 data, and/or automatically generated format. A set top box preferably includes digital trick play effects, and incorporated digital rights management features.

Ergonomic man-machine interface incorporating adaptive pattern recognition based control system

Abstract: An adaptive interface for a programmable system, for predicting a desired user function, based on user history, as well as machine internal status and context. The apparatus receives an input from the user and other data. A predicted input is presented for confirmation by the user, and the predictive mechanism is updated based on this feedback. Also provided is a pattern recognition system for a multimedia device, wherein a user input is matched to a video stream on a conceptual basis, allowing inexact programming of a multimedia device. The system analyzes a data stream for correspondence with a data pattern for processing and storage. The data stream is subjected to adaptive pattern recognition to extract features of interest to provide a highly compressed representation which may be efficiently processed to determine correspondence. Applications of the interface and system include a VCR, medical device, vehicle control system, audio device, environmental control system, securities trading terminal, and smart house. The system optionally includes an actuator for effecting the environment of operation, allowing closed-loop feedback operation and automated learning.

Image indexing using color correlograms

Abstract: We define a new image feature called the color correlogram and use it for image indexing and comparison. This feature distills the spatial correlation of colors, and is both effective and inexpensive for content-based image retrieval. The correlogram robustly tolerates large changes in appearance and shape caused by changes in viewing positions, camera zooms, etc. Experimental evidence suggests that this new feature outperforms not only the traditional color histogram method but also the recently proposed histogram refinement methods for image indexing/retrieval.

Digital wavefront measuring interferometer for testing optical surfaces and lenses

Abstract: A self-scanned 1024 element photodiode array and minicomputer are used to measure the phase (wavefront) in the interference pattern of an interferometer to lambda/100. The photodiode array samples intensities over a 32 x 32 matrix in the interference pattern as the length of the reference arm is varied piezoelectrically. Using these data the minicomputer synchronously detects the phase at each of the 1024 points by a Fourier series method and displays the wavefront in contour and perspective plot on a storage oscilloscope in less than 1 min (Bruning et al. Paper WE16, OSA Annual Meeting, Oct. 1972). The array of intensities is sampled and averaged many times in a random fashion so that the effects of air turbulence, vibrations, and thermal drifts are minimized. Very significant is the fact that wavefront errors in the interferometer are easily determined and may be automatically subtracted from current or subsequent wavefrots. Various programs supporting the measurement system include software for determining the aperture boundary, sum and difference of wavefronts, removal or insertion of tilt and focus errors, and routines for spatial manipulation of wavefronts. FFT programs transform wavefront data into point spread function and modulus and phase of the optical transfer function of lenses. Display programs plot these functions in contour and perspective. The system has been designed to optimize the collection of data to give higher than usual accuracy in measuring the individual elements and final performance of assembled diffraction limited optical systems, and furthermore, the short loop time of a few minutes makes the system an attractive alternative to constraints imposed by test glasses in the optical shop.