E Tanaka

HAMAMATSU Photonics K.K., Hamamatu, Shizuoka, Japan

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Publications (49)52.56 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: A time-of-flight (TOF) multi-probe system has been developed to measure the distribution of positron-emitting tracers in the body. The system uses 16 (a pair of 8) detector probes, each of which is composed of a truncated pyramid BaF<sub>2</sub> crystal and a 26 mm diameter photomultiplier tube (Hamamatsu R5320). The average coincidence time resolution for possible 64 coincidence pairs is 180 ps FWHM, which corresponds to 2.7 cm in space. The system performance such as count rate and imaging capabilities were evaluated using phantoms. The results show that a low-cost positron imaging system can be constructed using the TOF detector probes. The system is designed to increase the number of detector probes up to 32 (a pair of 16) for a better imaging capability
    Nuclear Science Symposium and Medical Imaging Conference Record, 1995., 1995 IEEE; 11/1995
  • K Shimizu, N Satoh, H Uchida, E Tanaka
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    ABSTRACT: We are developing a time-of-flight (TOF) multiprobe imaging system, which is used to determine the distribution of the administered tracer substances labeled with positron emitting nuclides. A prototype system has eight detector probes, each that consists of a BaF<sub>2</sub> scintillator and a fast photomultiplier tube. The system construction is simple compared to positron emission tomographs by virtue of using TOF information of annihilation. We have studied the time resolution for different shapes of BaF<sub>2</sub> scintillators by Monte Carlo simulations and experiments, and found that truncated pyramid shaped crystals provided good time resolution with reasonable sensitivity. Coincidence time resolution of 180 to 200 ps were obtained with 16 combinations of the detectors in the system. An iterative algorithm for image reconstruction using TOF data was proposed. By introducing a proper deblurring algorithm into the image reconstruction process, the spatial resolution can be improved by a factor of two without significant amplification of noise, which corresponds to a spatial resolution of 1.5 cm
    Instrumentation and Measurement Technology Conference, 1994. IMTC/94. Conference Proceedings. 10th Anniversary. Advanced Technologies in I & M., 1994 IEEE; 06/1994
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    ABSTRACT: In the PET system a block detector, which is a position-sensitive photomultiplier (PMT) tube coupled to four arrays of 1.7-mm-wide BGO crystals, is utilized. Fifteen block detectors are positioned to form a 35-cm-diameter ring, with four BGO arrays coupled to each PMT. This provides four detector rings, giving the system a 7-slice imaging capability. The gantry head tilts up to +/-90 degrees , and is capable of moving up and down by 30 cm. These positioning capabilities allow flexibility and great ease of use in subject positioning. A gantry entrance size of 22 cm in diameter allows studies ranging from rats and mice to primates such as Rhesus and squirrel monkeys. The physical performance of the system has been evaluated.
    IEEE Transactions on Medical Imaging 02/1992; 11(4):577-80. · 4.03 Impact Factor
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    ABSTRACT: A high-resolution positron emission tomograph (PET) for brain studies has been developed. It consists of five detector rings (240 BGOs/ring). New multisegment photomultiplier tubes (PMTs) were adopted for the system with 5-mm-wide BGOs. The system is designed to examine a patient sitting or lying down on a chair/bed couch. The functions of PMT auto gain control and real-time image display are implemented in the system. The physical performance of the system was evaluated: the spatial resolution is 3.5 mm in the transaxial plane and 5.7 mm in the axial direction, and the total system sensitivity is 109 kcps/μCi/ml for a uniform phantom 20 cm in diameter with a pulse height threshold of 350 keV
    IEEE Transactions on Nuclear Science 05/1990; · 1.22 Impact Factor
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    ABSTRACT: A simple time-of-flight (TOF) positron imaging method is proposed in which the spatial resolution obtained with TOF information is improved by a novel iterative algorithm. The prototype has a pair of opposed detectors using BaF<sub>2</sub> (2×2×2 cm<sup>3</sup>) and photomultiplier tubes (18.5-mm diameter). The measured TOF resolution full width at half maximum was 330 ps, which corresponds to 5.0 cm of spatial resolution for source localization between the detectors. Eight iterations with the algorithm improve the spatial resolution by a factor of about two for a point source. The algorithm is based on modifications of a Bayesian deconvolution algorithm. For more complex sources, it takes more iterations (e.g. 80); however the algorithm is about five times faster than the original Bayesian algorithm
    IEEE Transactions on Nuclear Science 03/1989; · 1.22 Impact Factor
  • Kaku igaku. The Japanese journal of nuclear medicine 07/1987; 24(6):797-807.
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    ABSTRACT: This paper describes evaluation and correction of count rate characteristics of POSITOLOGICA II, a multi-slice whole body positron emission tomography system. The present study was performed using three phantoms; a 5 cm inner diameter, water-filled lucite cylinder, a 20 cm inner diameter, water-filled lucite cylinder and a chest phantom. After injection of high activity (about 1.85 GBq (50 mCi] of 13N ammonia into each phantom, rates of true coincidence, random coincidence and single photon detections were measured during decay of the isotope through more than two orders of magnitude of activity. At very high levels of activity, count rate characteristics of the system were saturated and limited to 660 kcps of total coincidence rate, which was the sum of rates in on-time and off-time windows, by the FIFO (first-in first-out) output frequency. Below those levels of activity the relationship between count loss and true coincidence rate was not unique but depended on the phantom configurations, suggesting that count loss correction using the above relationship was inadequate for quantitative study. However, the relationship between count loss and single rate was almost independent of the phantom configurations. Thus in conclusion count loss could be corrected using single rate for POSITOLOGICA II. A practical method of count loss correction was also proposed.
    Radioisotopes 05/1987; 36(5):221-6.
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    ABSTRACT: Single photon emission computed tomography (SPECT) systems are proposed which provide images with improved signal-to-noise ratio. The systems consist of gamma cameras equipped with collimators which view an object to be imaged with an increased sampling density in the vicinity of the center of a field-of-view. The detection systems produce weighted projection data. Evaluation was made with respect to noise characteristics in images resulting from such systems. Simulation studies showed that dual and quadruple camera systems equipped with a combination of fan beam collimators result in noise reduction of about 37% at the center of image and uniform noise over an image area, compared with systems equipped with parallel hole collimators. This suggests that the proposed systems have a possibility of improvement on quantitation of SPECT.
    IEEE Transactions on Nuclear Science 03/1987; · 1.22 Impact Factor
  • H Murayama, N Nohara, E Tanaka
    Kaku igaku. The Japanese journal of nuclear medicine 10/1986; 23(10):1351-60.
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    ABSTRACT: Feasibility of stationary positron emission tomography (PET) using discrete detectors has been investigated by simulation studies. To enable full utilization of detector resolution, a "bank array" of detectors is proposed and an EM algorithm is adopted for image reconstruction. The bank array consists of an odd number of detector banks arranged on a circular ring with a gap equal to one half the detector width. The EM algorithm [11] is used with some modifications for reducing the quantity of computation, improving the convergence speed, and suppressing statistical noise, so as to meet the present purpose. Simulation studies involving several phantoms show that the stationary PET with the new detector array provides image quality which is good enough for clinical applications. For fast dynamic studies with low spatial resolution, the convolution-backprojection method is efficient, but for high-resolution static imaging, resolution enhancement by an iterative method is required. Problems arising in the corrections for attenuation of photons and detector sensitivity, etc., are also discussed. A totally stationary PET avoids the mechanical problems associated with accurate movement of heavy assemblies and is particularly advantageous in gated cardiac imaging or in fast dynamic studies. Elimination of a scan along the detector plane allows a quick scan in the axial direction to achieve three-dimensional imaging with a small number of detector rings.
    IEEE Transactions on Medical Imaging 02/1986; 5(4):199-206. · 4.03 Impact Factor
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    ABSTRACT: A single ring high resolution positron CT for animal studies was developed which utilizes 64 gridded rectangular photomultipliers (l3mm square) and 128 rectangular Bismuth Germanate crystal (4mm wide, 10mm high and 20mm long). A photomultiplier is incorporated with a grid near the photocathode which controls photoelectron transport of half part of a tube. This enalbes us the identification of the fired crystal out of two coupled to a photomultiplier. Detector ring, animal port and field of view diameters are 265, 135 and 128mm, respectively. Detector arrangement was determined by POSITOLOGY. The spatial resolutions in fwhm after unfolding source spread (2mm dia.) were 2.2mm at center and 3.3mm (tangential) and 3.6mm(radial) at 60mm from the center. Hardware out-of-FOV event rejector was implemented which rejects events outside the field of view and reduces event rate by a factor of 3 in the case of calibration measurements.
    IEEE Transactions on Nuclear Science 03/1985; · 1.22 Impact Factor
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    ABSTRACT: Performance of positron emission computed tomographs having spatial resolution as high as 3 mm FWHM was analytically evaluated. Increases in widths of line spread functions due to positron range and angular deviation were estimated. The slice thickness should be thin in accordance with the resolution in transverse axial plane. Singles rate, true coincidence rate, and scattered coincidence rate with high resolution tomographs of small diameter detector rings were estimated for three types of thin slice collimators. Feasibility of high resolution positron tomographs with small detector rings was discussed with applications to animal study.
    IEEE Transactions on Nuclear Science 03/1985; · 1.22 Impact Factor
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    ABSTRACT: Twin BGO detectors and timing pulse shape discriminators for crystal identification have been developed for high spatial resolution positron emission tomography. Each detector consists of two BGO crystals and one single photomultiplier tube. The tube has a grid covering half the area of the photocathode window, and opposite to which stands one of the BGO crystals. The amplitude of the anode signals for the scintillation events in the grid side crystal is modulated by supplying negative pulses to the grid. Crystal identification is achieved by pulse shape discrimination for the detector signals.The design criteria of the electronic system and the performance are described. With suitable pulse shape discrimination, the erroneous positioning due to statistical noise is negligible and the coincidence time resolution for annihilation photon pairs is about 5.8 ns fwhm.
    Nuclear Instruments and Methods in Physics Research. 04/1984; 221(3):633–640.
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    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.
    IEEE Transactions on Nuclear Science 03/1983; · 1.22 Impact Factor
  • Kaku igaku. The Japanese journal of nuclear medicine 09/1982; 19(7):987-1000.
  • E Tanaka, N Nohara, T Tomitani, M Endo
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    ABSTRACT: The image-forming performance of multilayer positron tomographs for extended sources is evaluated analytically. The analysis is simplified by "rotation transform," by which three-dimensional photon detection problems are solved by two-dimensional treatment. Event rates of singles, unscattered true coincidence, and a single- and double-scattered coincidence are formulated for a uniform cylinder phantom as functions of various design parameters. Angle factors for Compton scattering and other parameters used in the evaluation are presented. Scatter components in projections and their effect on the reconstructed images are also evaluated. The scatter component in the reconstructed image depends critically on the detector ring radius, phantom radius, method of attenuation correction, etc. When the director radius is relatively small (40 or approximately 45 cm in diameter), the scatter/true ratio at the image center of a 20 cm diameter phantom may be larger than the scatter/true ratio in the event rates. Comparison with experimental data obtained with a head positron tomograph, POSITOLOGICA, showed reasonable agreement both in the total coincidence rates and in the scatter components in the images for a cylindrical phantom of 20 cm in diameter.
    Journal of Computer Assisted Tomography 05/1982; 6(2):350-64. · 1.58 Impact Factor
  • Kaku igaku. The Japanese journal of nuclear medicine 04/1982; 19(2):217-22.
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    ABSTRACT: Evaluation of slice shield collimators is carried out using theoretical event rate formulas. This approach permits calculation of system performance in terms of sensitivity, scatter fraction, and high-counting rate characteristics. Electronics counting efficiency is also taken into account. A rational approach to optimal design is presented along with design examples. Effectiveness of collimator replacement is suggested. A system using sub-collimator with relatively small detector ring radius is proposed. It achieves a level of performance similar to that of a conventional collimator system with large ring radius.
    IEEE Transactions on Nuclear Science 03/1982; · 1.22 Impact Factor
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    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.
    IEEE Transactions on Nuclear Science 03/1982; · 1.22 Impact Factor
  • M Endo, T A Iinuma, E Tanaka, Y Tateno
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    ABSTRACT: The effects of correction function on image characteristics were studied experimentally for a positron CT device Positologica. Correction functions were obtained by smoothing the Shepp and Logan function by convolution of Gaussian functions. Signal-to-noise ratio (SNR) and spatial resolution were measured for phantoms and related to the magnitude of smoothing. The relation between SNR and spatial resolution is also discussed. Some suggestions are made to indicate how to select correction functions for clinical images. A flow of data processing for Positologica is described together with an outline of its hardware.
    European Journal of Nuclear Medicine 02/1982; 7(3):130-6.

Publication Stats

339 Citations
52.56 Total Impact Points

Institutions

  • 1992–1995
    • HAMAMATSU Photonics K.K.
      Hamamatu, Shizuoka, Japan
  • 1963–1987
    • National Institute of Radiological Sciences
      Tiba, Chiba, Japan
  • 1982
    • Hitachi, Ltd.
      Edo, Tōkyō, Japan