Ken Ueda

Bio: Ken Ueda 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 12 publications receiving 164 citations.

Positologica: A Positron ECT Device with a Continuously Rotating Detector Ring

Abstract: A rotary positron emission computed tomography device is developed for human brain and animal studies. The device utilizes 64 rectangular BGO detectors arranged at unequal spacing on a circular ring. The detector ring is continuously rotated at a constant speed of 60 rpm or less. This single continuous motion of the ring with the detector array provides excellent sampling characteristics and high detector redundancy. The device has a field of view 24 cm in diameter with a slice thickness adjustable from 1 cm to 2 cm. Measured width of system response to a 2 mm diameter line source is 5.8 mm FWHM at the center and less than 9 mm FWHM within a circle 16 cm in diameter. Measured sensitivity including scattered coincidence events is about 17 kcps/pCi/ml for a 20 cm diameter water phantom and 2 cm thick slice.

Characteristics of a gamma‐ray detector using a bismuth germanate scintillator

Abstract: Characteristics of a gamma‐ray detector that utilizes a 24×24×15‐mm3 bismuth germanate (BGO) scintillator are measured. Fluorescent light output measured with a BGO crystal coupled to a R1306 photomultiplier (Hamamatsu TV) is found to be 15% that of a NaI(T1) scintillator for incident photons of a given energy. The FWHM of the time spectrum, measured with two BGO crystals coupled to R329‐2 photomultipliers, is equal to 2.0 ns for a 68Ge–68Ga source at room temperature.

Design Consideration for a Continuously Rotating Positron Computed Tomograph

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.

Radiation imaging sensor

Abstract: A radiation imaging sensor including laminate structure of a phosphorescent layer, a light-transmissive electrode, a photoconductor layer, an insulating layer and an electrode, an applied voltage to the photoconductor layer through the light-transmissive electrode and the electrode is increased sufficiently so that light emitted from the phosphorescent member causes avalanche multiplicaton of the electrons and/or positive holes generated in the photoconductor layer by field sweep inside the photoconductor layer.

Performance Study of Whole-Body, Multislice Positron Computed Tomograph POSITOLOGICA-II

Abstract: A 3-detector ring, 5-slice whole-body positron CT has been developed and is being tested. The PCT, POSITOLOGICA-II, has a total of 480 BGO's (160/ring), and employs continuous rotation scan (0.5rps). By using a 15mm wide BGO, a 9.2mm FWHM spatial resolution for reconstructed image is obtained at the center of FOV. Measured phantom diameter dependence of the true count rate shows good agreement with theoretically anticipated characteristics, including maximum sensitivity at around 30cm dia. Sensitivities for 20cm dia. phantom are 28 and 38 kcps/?Ci/ml for in-plane and cross-plane, respectively, including scattered coincidences. Relative system detection efficiency measured with a line source at FOV center is 96% at 15ns time window (90% at 12ns), basing on 100% efficiency in 20-24ns.

Measuring PET scanner sensitivity: relating countrates to image signal-to-noise ratios using noise equivalents counts

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 >

Non-proportionality in the scintillation response and the energy resolution obtainable with scintillation crystals

Abstract: A review and new data are presented on the absolute photon yield emitted by "classical" (NaI(Tl/sup +/), CsI(Tl/sup +/), CsI(Na/sup +/), CaF/sub 2/(Eu/sup 2+/), Bi/sub 4/Ge/sub 3/O/sub 12/, and CdWO/sub 4/) and "modern" (BaF/sub 2/, Gd/sub 2/SiO/sub 5/(Ce/sup 3+/), YAlO/sub 3/(Ce/sup 3+/), Lu/sub 2/SiO/sub 5/(Ce/sup 3+/), Lu/sub 3/Al/sub 5/O/sub 12/(Sc/sup 3+/), and K/sub 2/LaCl/sub 5/(Ce/sup 3+/)) scintillation crystals after absorption of X-rays and /spl gamma/-rays of energies ranging from 5 keV to 1 MeV. Factors influencing the energy resolution with which high energy photons can be detected with scintillator-photomultiplier combinations are reviewed. Attention is especially focused on the effects of nonproportionality in the scintillation response on the energy resolution.

Inorganic-scintillator development

Abstract: A review is presented of recent inorganic scintillator R&D. Attention is focused on Ce doped gamma-ray and thermal-neutron scintillators for counting applications.

Study of Cerebral Function with Positron Computed Tomography

Abstract: Abbreviations: ACD, Annihilation coincidence detection; BGO, bismuth germanate; CBF, cerebral blood flow; CBV, cerebral blood volume; CMG, 3-(11C)-methyl-D-glucose; CMRGlc, cerebral metabolic rate for glucose; CMR02, cerebral metabolic rate for oxygen; CsF, cesium fluoride; CT, computed tomography; DG, deoxyglucose; FDG, 2-fluoro-2-deoxy-d-glucose; LC, lumped constant; OEF, oxygen extraction fraction; PCT, positron computed tomography; PETT, positron emission transaxial tomography; PT, physiological tomography.

Cerium‐activated Gd2SiO5 single crystal scintillator

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.