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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: In this paper, the authors proposed a continuously rotating positron ECT system, in which the detectors are arranged on a circular ring with "non-uniform" spacing so as to provide much finer sampling interval in the projections than the conventional circular ring system.
Abstract: This paper proposes a continuously rotating positron ECT system, in which the detectors are arranged on a circular ring with "non-uniform" spacing so as to provide much finer sampling interval in the projections than the conventional circular ring system. The address signals on the coincidence events are read out through a rotary photo-coupler, and the detector system can be rotated at a desired speed. Suitable detector arrangements are searched which provide sufficiently fine sampling interval with reasonable sampling density uniformity. Assuming about 50 detectors are arranged on a circle, the sampling characteristics of various detector arrangements have been examined. An iterative search method has also been applied to find a reasonable arrangement. The best arrangement has been obtained by the iterative method. It has an effective sampling interval of the order of (1/200)R, where R is the radius of the detector array, and the sampling density uniformity after 5-point smoothing is -7.8 ˜/spl I.chemo/18 % in the range of /spl I.chemo/ R/2.

35 citations

Journal ArticleDOI
TL;DR: In this article, the design of a whole-body, multislice Positron CT with three detector rings, 160 BGO crystal/ring, and a continuously rotating scan is described.
Abstract: Design consideration for a whole-body, multislice Positron CT having 3 detector rings, 160 BGO crystal/ring, and a continuously rotating scan is described. The one detector ring has 40 "BGO Quad-detectors", each of which consists of 4 BGO crystals and two photomultipliers. Improvements in the BGO crystal and the photomultiplier have been accomplished. Geometrical configuration of the collimator was determined through optimization of the main performances of both the inplane and cross-plane images, utilizing the formulae for a cylindrical phantom with uniform activity. A continuously rotating scan (0.5-1rps) with unequally spaced the Quad-detector units is used. Along with this scan, a 32-channel rotary photo-coupler was developed for contact-free data transmission.

21 citations

Patent
29 Sep 1980
TL;DR: In this article, an apparatus for detecting the location of incident radiation comprises at least one pair of assembly comprised of a scintillation crystal consisting of a plurality of crystal segments, and a pair of photo-multiplier tubes optically coupled to the crystal so as to be able to detect scintillations produced in any one of these crystal segments.
Abstract: An apparatus for a detecting the location of incident radiation comprises at least one pair of assembly comprised of a scintillation crystal consisting of a plurality of crystal segments, a pair of photo-multiplier tubes optically coupled to the scintillation crystal so as to be able to detect a scintillation produced in any one of these crystal segments. These plural crystal segments are coupled to each other in such manner that any scintillation produced in any single crystal segment will cause the photo-multiplier tubes to deliver substantially a same output irrespective of the illuminating position within this crystal segment, and also that scintillations produced in the respective crystal segments will cause the photo-multiplier tubes to deliver outputs which are different in level for the respective crystal segments.

19 citations

Patent
30 Mar 1979
TL;DR: In this article, the authors proposed to increase the propagation efficiency of light between the scintillator and the photo detector by forming the silicon nitride film on the inorganic scintillation surface with plasma glow discharge.
Abstract: PURPOSE: To increase the propagation efficiency of light between the scintillator and the photo detector, by forming the silicon nitride film on the inorganic scintillator surface with plasma glow discharge. CONSTITUTION: Since the inorganic substance scintillator 1 such as NaI(Tl), CsI(Tl), and Bi 4 Ge 3 O 12 has greater refractive index as 1.85W2.15, the reflection loss on the surface of light is greater. The film 2 of silicon nitride is vacumm- evaporated on the surface of the scintillator with plasma glow discharge. The silicon nitride film 2 gives the refractive index of 1.5W2.1 when the temperature of substrate is changed in the range of 40W300°C. The surface reflection of the scintillator can be reduced by changing continuously the refractive index of silicon evaporation film evaporated on the surface of scintillator 1 or taking it to a suitable value for the prevention of reflection. COPYRIGHT: (C)1980,JPO&Japio

16 citations

Patent
28 Mar 1980
TL;DR: In this article, an apparatus for effecting positron emission computed tomography comprises rows of a plurality of arrays of detectors arranged rotatably around a center of rotation in such way that at least one of the detectors in each array is desposed at an irregular position relative to the rest of detectors in the array, and that, for each revolution of the row through an angle of 360°/n (wherein: n represents an odd number of 3 or larger), each array of detectors will assume exactly the position occupied by its adjacent array till the revolution takes place.
Abstract: of the disclosure An apparatus for effecting positron emission computed tomography comprises rows of a plurality of arrays of detectors arranged rotatably around a center of rotation in such way that at least one of the detectors in each array is desposed at an irregular position relative to the rest of detectors in the array, and that, for each revolution of the row through an angle of 360°/n (wherein: n represents an odd number of 3 or larger), each array of detectors will assume exactly the position occupied by its adjacent array till the revolution takes place.

15 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