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Kenji Ishimatsu

Bio: Kenji Ishimatsu is an academic researcher from Hitachi. The author has contributed to research in topics: Scintillator & Scintillation. The author has an hindex of 8, co-authored 27 publications receiving 200 citations. Previous affiliations of Kenji Ishimatsu include National Institute of Radiological Sciences.

Papers
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Journal ArticleDOI
TL;DR: To increase the detection efficiency and improve the spatial resolution, a coded-aperture imaging method is applied to nuclear medicine, which consists of nine pinholes arranged in a square grid.
Abstract: To increase the detection efficiency and improve the spatial resolution, a coded-aperture imaging method is applied to nuclear medicine. The aperture consists of nine pinholes arranged in a square grid. Three kinds of coding are sequentially used to record the same number of projections including parallax and overlap. The overlapped images are partially separated, and good tomograms of a ring phantom and a human myocardium are reconstructed using a modified backprojection algorithm with variable damping factor.

3 citations

Patent
Kenji Ishimatsu1, Hideho Tabuchi1
30 Jun 1969
TL;DR: In this paper, the stored charge density pattern on the surface of a direct-view-type storage tube target and this pattern is then reproduced on the screen of said storage tube as a visible image which in turn is reproduced on a photographic film.
Abstract: A photographing method wherein the distributed image of an object to be photographed is initially stored in the form of a stored charge density pattern on the surface of a direct-view-type storage tube target and this pattern is then reproduced on the screen of said storage tube as a visible image which in turn is reproduced on a photographic film. In the production of the image, the value for a bias voltage to be applied to the target of the storage tube is caused to change continuously or gradually from a level at which no pattern area can be reproduced, no matter how high the stored charge density is, up to a level at which all the pattern areas are reproducible at the same time, whereby the higher the stored charge density of a pattern area is, the longer the exposure time of a film becomes (with a consequent increase in the amount of exposure). According to this method, a well-contrasted picture is obtainable through a very simple operation.

3 citations

Patent
08 Jul 1980
TL;DR: In this article, the authors proposed a scheme to make it possible to transfer several signals at high S/N by supplying light from light emitting elements to photo detecting elements at constant intervals in sequence.
Abstract: PURPOSE:To make it possible to transfer several signals at high S/N by supplying light from light emitting elements to photo detecting elements at constant intervals in sequence. CONSTITUTION:On the circumference of body 2 of revolution, a needed number of semiconductor light emitting elements 3 are distributed at even intervals. A PCM-ed pulse signal from signal source 2 lets light emitting element 3, corresponding to a code, emit light. Two photo detecting elements 4 and 4' are provided as stoppers. When light emitting element 3 moves to a halfway point between photo detecting elements 4 and 4' to minimize output signals of the both, change-over method 5 is changed over. As an output signal from change-over method 5, a PCM-ed code signal source 2 is regenerated and supplied to signal processing circuit 7 to lead its output out.

3 citations


Cited by
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Journal ArticleDOI
TL;DR: It is demonstrated that, compared to the Alderson brain phantom, the standard 20-cm cylinder is a poor predictor of count rate performance for PET brain imaging.
Abstract: True coincidence count (TCC) and noise equivalent count (NEC) curves were measured with a standardized 20-cm-diameter nylon cylinder for five different CTI/Siemens PET (positron emission tomography) scanners with several scanner-collimator combinations: (1) 831/08-12 with 1-mm collimator septa; (2) 933/08-12 and 933/08-16 with 3 to 1-mm tapered collimator septa; and (3) 931/08-12 with 3 to 1-mm tapered and a 1-mm collimator septa and the 931/08-16 with 3 to 1-mm tapered collimator septa In addition, TCC and NEC curves on the 933/08-12 were compared with those from an Alderson brain phantom In general, it is found that the TCC curves indicated peak count rates and activity levels that were as much as 50% higher than the corresponding values from NEC curves The primary factor causing this difference is the noise effect of the randoms component It is demonstrated that, compared to the Alderson brain phantom, the standard 20-cm cylinder is a poor predictor of count rate performance for PET brain imaging >

548 citations

Journal ArticleDOI
TL;DR: Coded aperture imaging in high energy astronomy represents an important technical advance in instrumentation over the full energy range from X-to γ-rays and is playing a unique role in those spectral ranges where other techniques become ineffective or impracticable due to limitations connected to the physics of interactions of photons with matter.
Abstract: Coded aperture imaging in high energy astronomy represents an important technical advance in instrumentation over the full energy range from X- to γ-rays and is playing a unique role in those spectral ranges where other techniques become ineffective or impracticable due to limitations connected to the physics of interactions of photons with matter. The theory underlying this method of indirect imaging is of strong relevance both in design optimization of new instruments and in the data analysis process. The coded aperture imaging method is herein reviewed with emphasis on topics of mainly practical interest along with a description of already developed and forthcoming implementations.

409 citations

Journal ArticleDOI
TL;DR: In this article, the light output was 1.3 times larger than that of the best Bi4Ge3O12, and the decay constant was 60 ns at room temperature.
Abstract: Cerium‐activated phosphors are characterized by their fast luminescence decay. Gadolinium orthosilicate (Gd2SiO5) is a material possessing a high atomic number, and can also play host to the cerium activator. Cerium‐doped Gd2SiO5 single crystals were grown by the Czochralski technique, and their luminescence properties were examined. The light output was 1.3 times larger than that of the best Bi4Ge3O12, and the decay constant was 60 ns at room temperature.

342 citations

Patent
02 Jun 1983
TL;DR: In this paper, the selected internal skeletal structure is measured by subjecting the body to radiant energy to produce radiant energy responses that are detected to obtain representations delineating the skeletal structure.
Abstract: Non-invasive method of forming prostheses of skeletal structures internal to a body for use in reconstructive surgery. The selected internal skeletal structure is measured by subjecting the body to radiant energy to produce radiant energy responses that are detected to obtain representations delineating the skeletal structure. Three dimensional coordinate data defining the skeletal structure is generated from the obtained representations. The coordinate data is employed to control a sculpting tool to form the prosthesis.

315 citations

Journal ArticleDOI
TL;DR: The method, the iterative image space reconstruction algorithm (ISRA), is able to reconstruct data from a scanner with a spatially variant point spread function in less time than other proposed algorithms.
Abstract: The trend in the design of scanners for positron emission computed tomography has traditionally been to improve the transverse spatial resolution to several millimeters while maintaining relatively coarse axial resolution (1-2 cm). Several scanners are being built with fine sampling in the axial as well as transverse directions, leading to the possibility of the true volume imaging. The number of possible coincidence pairs in these scanners is quite large. The usual methods of image reconstruction cannot handle these data without making approximations. It is computationally most efficient to reduce the size of this large, sparsely populated array by back-projecting the coincidence data prior to reconstruction. While analytic reconstruction techniques exist for back-projected data, an iterative algorithm may be necessary for those cases where the point spread function is spatially variant. A modification of the maximum likelihood algorithm is proposed to reconstruct these back-projected data. The method, the iterative image space reconstruction algorithm (ISRA), is able to reconstruct data from a scanner with a spatially variant point spread function in less time than other proposed algorithms. Results are presented for single-slice data, simulated and actual, from the PENN-PET scanner.

241 citations