Japanese Journal of Medical Physics (Igakubutsuri)
Online ISSN : 2186-9634
Print ISSN : 1345-5354
ISSN-L : 1345-5354
Volume 22, Issue 4
Displaying 1-13 of 13 articles from this issue
  • Kiyonari Inamura
    2002 Volume 22 Issue 4 Pages 196-209
    Published: December 31, 2002
    Released on J-STAGE: September 24, 2012
    JOURNAL FREE ACCESS
    Present status of development of flat panel detectors and their clinical application in the world have been surveyed, and future trends are also explored especially in the field of material researches and methods of manufacturing. Also the importance of role of medical physicists on user side is described because characteristic physics measurement of a detector assembly is unavoidable and essential in quality assurance in clinical routine and acceptance test in hospitals.
    Even though physics measurements and clinical evaluations on flat panel detectors have shown remarkable progress and advances in these several years, future problems of cost down in manufacturing and quality assurance to prevent individual differences between detector assemblies must be resolved.
    Results of evaluation in m ammography, chest radiography, fluoroscopy for cardiovascular examination, bone tumor examination and radiotherapy application indicate that flat panel detectors are future promising materials. Their systematic operation is contributing to heighten accuracy of image examinations and preciseness of radiation therapy. Encouragement to medical physicists relevant to flat panel detectors is also raised in this paper.
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  • Yoshiharu Higashida
    2002 Volume 22 Issue 4 Pages 210-215
    Published: December 31, 2002
    Released on J-STAGE: September 24, 2012
    JOURNAL FREE ACCESS
    In our country, the introduction of flat panel detector is carried out in the diagnosis region since before several years. In flat panel detector with the high image characteristic, large expectation is being placed. In this paper, image chara cteristic of flat panel detector and effectiveness of clinical application were reviewed.
    It is anticipated that flat panel detector with the excellent image characteristic gives large effect in the radiological diagnosis.
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  • State-of-the-art and future prospects
    Tatsuya Yamazaki
    2002 Volume 22 Issue 4 Pages 216-226
    Published: December 31, 2002
    Released on J-STAGE: September 24, 2012
    JOURNAL FREE ACCESS
    A flat -panel detector (FPD) is a long awaited technology to implement the digital X-ray imaging technology into the radiological department. This paper describes the state-of-the-art technology and future prospects on the FPD technology.
    State -of -the -art technology was reviewed taking the CXD I series as an example. Several FPD-based systems have been introduced into the Japanese market since CXDI-11 opened it in November 1998. Accompanying CXDI-C2 for control, CXDI-22for table position and CXDI-31 for portable, the CXDI series fulfils the requirement of the radiography room being a fully digitalized room.
    The FPD on the CXDI series is comprised of a scintillator (Gd2O2S: Tb3+) as a primary sensor in which the X ray is captured and an amorphous silicon detector (LANMIT) as a secondary sensor in which the fluorescent light is detected. Since the scintillator is identical to that of the screen-film systems, it can be said as proven, durable and chemically stable and it is expected to produce the same image quality as the screen -film systems. CXDI 31, a portable FPD -based system, was developed targeting thinner dimensions, lightweight, durability and high spatial resolution. Thoroughly re-designing the mechanical structure and reducing the power consumption at the readout IC realized thinner dimensions. Introducing the portable note PC technologies successfully combined lightweight with durability. Improving the sensor process and re designing the layout made the sensor high resolution without compromising the signal to - noise ratio.
    Future prospects were overviewed in the aspect of technology and applications. Sensitivity, spatial resolution, frame rate and portability were described as the upcoming technology. Increasing gain and reducing noise will realize higher sensitivity, especially by adopting the PbI2, HgI2 or such photoconductor materials as the primary sensor. Pixelized amplifier will also achieve higher sensitivity. Layered sensor designed such that TFT layer and sensitive layer are constructed separately will decrease the pixel pitch lower than 100μm. The FPD has been applied in radiography, mammography and angiography. It w ill expand the applications into low - dose fluoroscopy to replace the X-ray image intensifiers and into cone - beam computer tomography.
    What the FPD brought was mainly the efficient workflow of the X-ray technologist. However, diagnosis efficiency and patient benefit must be improved further more by combining the FPD technology into computer-aided diagnosis, tele-radiography or other IT-based technologies. Such prospects may come true in the near future.
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  • Shinichi Yamada
    2002 Volume 22 Issue 4 Pages 227-231
    Published: December 31, 2002
    Released on J-STAGE: September 24, 2012
    JOURNAL FREE ACCESS
    We introduced digital X- ray diagnostic systems with Flat panel detector both in general X-ray systems and in Angiography systems. Our introduced Flat Panel Detector has the latest technology and has Cesium Iodide (CsI) that absorbs X-ray energy and generates visible light. Detected light signals make digital X-ray images. CsI is the most important material because its absorption rate of X-ray influences the strength of output digital signal. The purpose in this paper is checking that is latest Flat Panel Detector pulls out enough capability CsI has. Especially the thickness of CsI relates to X-ray absorption. X-ray absorption rate depended on the thickness of CsI was calculated by using simulated X-ray model and the future direction of Flat Panel Detector system was discussed.
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  • Masao Matsumoto, Iori Sumida, Tadamitsu Ideguchi, Yasuyuki Kawaji, Kaz ...
    2002 Volume 22 Issue 4 Pages 232-245
    Published: December 31, 2002
    Released on J-STAGE: September 24, 2012
    JOURNAL FREE ACCESS
    We measured and evaluated digital, pre-sampling and overall imaging properties (characteristic curve, modulation transfer function (MTF), Wiener spectrum (WS), noise equivalent quanta (NEQ) ) for Cannon's flat-panel detector (FPD), Fuji computed radiography (FCR) and screen-film (S/F) systems, respectively. First, the digital and overall characteristic curves of FPD and FCR systems were more wide dynamic range than that of the S/F system. Second, the pre-sampling and overall MTF of FPD system were better than those of FCR system a little at lower spatial frequencies than 0.8mm-1, but the overall MTF of FPD and FCR systems were worse than that of S/F system a little at all spatial frequencies. Third, the digital and overall WS of FPD system were similar or better than those of FCR system, but the overall WS of FPD and FCR systems were worse than that of S/F system. Fourth, the pre-sampling and overall NEQ of FPD system were better than those of FCR system a little at lower spatial frequencies than 1.6mm-1, but the overall NEQ of FPD and FCR systems were worse than that of S/F system at all spatial frequencies. Comparison of chest phantom images showed that the FPD produced images with quality comparable to or higher than those of the FCR system. From these results, we can expect that the FPD is useful machine by using digital image processing and so on in the radiology department.
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  • Akira Yoshida, Satoru Nakamura, Sadamitsu Nishihara, Chiyuki Kohama, A ...
    2002 Volume 22 Issue 4 Pages 246-254
    Published: December 31, 2002
    Released on J-STAGE: September 24, 2012
    JOURNAL FREE ACCESS
    We report the physical imaging properties of a flat panel detector(FPD) designed for radiographic imaging applications(Revolution XQ/i digital chest imaging system, G. E. Medical Systems). The imaging properties of the detector were evaluated through measurements of the characteristic curve, modulation transfer function(MTF), and Wiener spectrum.
    The digital characteristic curves of the FPD system were measured for the two tube voltages(80kV and 120kV). They showed that the correlation between the pixel values of FPD and the incident exposure to the FPD was a linear correlation. The dynamic range of characteristic curves had a range from about 0.003 to 2 μ C/kg at the exposure. The presampling MTFs for different tube voltage were almost the same, when we measured the MTFs at 80kV and 120kV. And also, there was no significant difference between the MTFs measured with the slit in the direction parallel to the horizontal direction and with the slit in the perpendicular direction. The relative resolution of the FPD system was a 46% higher than that of ST V imaging plate of FCR(Fuji Computed Radiography) system at 2 cycles/mm. The digital Wiener spectrum of the FPD system was about 1/10 lower than that of the CR system. Thus the FPD system can provide superior imaging performance due to both high resolution and low noise.
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  • Kenji Okusako, Masachika Shogaki, Kouji Yokoyama, Takayoshi Ogawa, Kat ...
    2002 Volume 22 Issue 4 Pages 255-263
    Published: December 31, 2002
    Released on J-STAGE: September 24, 2012
    JOURNAL FREE ACCESS
    We had the chance of clinical studies by new proto-type Digital Subtraction Angiography (DSA) System with the Flat Panel Detector (FPD).
    That system has two types of detector, FPD and I. I. -CCD camera, and we can compare with image quality in clinical.
    We measured and discussed about the physical characteristic data of both detectors. Up to physical characteristic evaluation, FPD has good MTF and SNR performance, comparing with I.I.-CCD camera. In clinical evaluation, DSA image of FPD was superior to that of I. I. -CCD camera by visual comparison of medical doctors. Finally we discussed about the feasibility of replacement of detectors. We expect that DSA system will accept FPD in near future.
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  • Ogata Yuji, Masao Matsumoto, Koji Suekane
    2002 Volume 22 Issue 4 Pages 264-275
    Published: December 31, 2002
    Released on J-STAGE: September 24, 2012
    JOURNAL FREE ACCESS
    We measured and evaluated digital, pre-sampling and overall imaging properties (characteristic curve, Modulation Transfer Function (MTF), Wiener spectrum(WS), Noise Equivalent Quanta(NEQ) and Detective Quantum Efficiency(DQE)) for Hologic's direct type and Cannon's indirect type of Flat-Panel Detector(FPD). First, the digital and overall characteristic curves of both types of FPD were more wide dynamic range than that of the S/F system. Second, the pre-sampling and overall MTF of the direct-type FPD system were superior to those of the indirect-type FPD system. Third, for identical exposures, the digital and overall WS of the direct-type FPD system were similar or worse than those of the indirect-type FPD system, and for larger exposure, the digital WS of the both types of FPD system were smaller, but the overall WS of the both types of FPD systems were larger. Fourth, the digital and overall NEQ and DQE of the direct-type FPD system were worse than those of the indirect-type- FPD system at lower spatial frequencies than 1.75∼2.0mm-1, but were worse at higher spatial frequencies than 1.75∼2.0mm-1.
    We show radiographs made with the direct type of FPD system. Radiogr aphs of square wave chart show the difference in MTF and contrast of the both types of FPD systems. As the result of evaluation of radiographs of chest phantom in point of noise by radiologists and radiological technologists, the direct type of FPD system needed double or more exposure dose than own standard condition, this dose was same as the indirect-type FPD system. And radiologists evaluated radiographs of human body, spatial resolution was very good, but contrast was much more likely to high at standard parameter. Therefore we have to consider exposure condition and image processing for the direct type of FPD system.
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  • Yoshiharu Sukenobu, Michihiro Sasagaki, Norio Hirabuki, Hiroaki Naito, ...
    2002 Volume 22 Issue 4 Pages 276-286
    Published: December 31, 2002
    Released on J-STAGE: September 24, 2012
    JOURNAL FREE ACCESS
    There are many cases in which picture archiving and communication systems (PACS) are built with old type existing modalities with no DICOM output. One of the methods for interfacing them to the PACS is to implement video capture (/ frame grabber) equipment. This equipment takes analog video signal output from medical imaging modalities, and amplitude of the video signal is A/D converted and supplied to the PACS.
    In this report, we measured and evaluated the accuracy at which this video capture equipment could capture the image. From the physical evaluation, we found the pixel values of an original image and its captured image were almost equal in gray level from 20% 90%. The change in the pixel values of a captured image was ± 3 on average. The change of gray level concentration was acceptable and had an average standard deviation of around 0.63. As for resolution, the degradation was observed at the highest physical level. In a subjective evaluation, the evaluation value of the CT image had a greade of 2.81 on the average (the same quality for a reference image was set to a grade of 3.0). Abnormalities in heads, chests, and abdomens were judged not to influence diagnostic accuracy. Some small differences were seen when comparing captured and reference images, but they are recognized as having no influence on the diagnoses.
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  • Kazuhiro Koshino, Shigehito Suzuki, Minoru Sotoda
    2002 Volume 22 Issue 4 Pages 287-301
    Published: December 31, 2002
    Released on J-STAGE: September 24, 2012
    JOURNAL FREE ACCESS
    A new predictive technique for lossless compression is applied to CT and MR images in order to achieve high compression in the lossless mode. To accomplish this, a prediction value was obtained by assuming the horizontal and vertical components of each pixel. Wide and narrow predictive coding modes were adaptively selected to achieve an accurate prediction. The performance of the predictive technique was compared with the performance of four representative compression techniques in the lossless mode, using different types of CT and MR image sets with different bit rates. Overall, the proposed predictive technique yielded the best compression, particularly with the lower bit-rate images tested. While the compression results are largely dependent on the images used, the results confirm the strong potential of the proposed predictive technique as a strategy for obtaining high lossless compression in medical images.
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  • Kiyofumi Haneda, Tokuo Umeda, Tadashi Koyama, Hajime Harauchi, Kiyonar ...
    2002 Volume 22 Issue 4 Pages 302-317
    Published: December 31, 2002
    Released on J-STAGE: September 24, 2012
    JOURNAL FREE ACCESS
    The target of our study is to establish the methodology for analyzing level of security requirements, for searching suitable security measures and for optimizing security distribution to every portion of medical practice. Quantitative expression must be introduced to our study as possible for the purpose of easy follow up of security procedures and easy evaluation of security outcomes or results.
    Results of system analysis by fault tree analysis (FTA) clarified that subdivided system elements in detail contribute to much more accurate analysis. Such subdivided composition factors very much depended on behavior of staff, interactive terminal devices, kinds of service, and routes of network. As conclusion, we found the methods to analyze levels of security requirements for each medical information systems employing FTA, basic events for each composition factor and combination of basic events. Methods for searching suitable security measures were found. Namely risk factors for each basic event, number of elements for each composition factor and candidates of security measure elements were found. Method to optimize the security measures for each medical information system was proposed, Namely optimum distribution of risk factors in terms of basic events were figured out, and comparison of them between each medical information systems became possible.
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  • Tomoyuki Hasegawa, Hideo Murayama, Hajime Matsuura, Taiga Yamaya, Shuj ...
    2002 Volume 22 Issue 4 Pages 318-326
    Published: December 31, 2002
    Released on J-STAGE: September 24, 2012
    JOURNAL FREE ACCESS
    We analyzed basic physics characteristics of body-shields which have been considered for screening out radioactivity outside the field of view (OFOV) in positron emission tomography (PET). Phantom experiments were performed with simple rectangular body-shields. A Monte Carlo simulation technique was used to analyze the experimental results and to simulate cases that were not examined experimentally. It was confirmed that the body-shields effectively reduced unwanted radiations from OFOV radioactivity for one of the latest commercial PET scanners, the ECAT EXACT HR+. The geometrical conditions were the most important factor in determining the shielding effect. The shield thickness should be large enough to keep the shield scatter component low. The body-shield should be carefully designed to minimize the gap between the body shield and radioactive distribution as much as possible to maximize the shielding effects, and to be applicable to clinical diagnoses.
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  • Yuichiro Yamamoto, Hirokazu Namikawa, Kiyonari Inamura
    2002 Volume 22 Issue 4 Pages 327-333
    Published: December 31, 2002
    Released on J-STAGE: September 24, 2012
    JOURNAL FREE ACCESS
    We designed a new medical information event model and developed a time oriented data warehouse based on the model. Here, the medical information event in a basic data unit is handled by a medical information system. The timing of decision making and treatment for a patient in the processing of his medical information is sometimes very critical. The time oriented data warehouse was developed, to provide a search feature on the time axis. Our medical information event model has a unique simple data structure. PC ORDERING2000 developed by NEC, which used Oracle, had about 600 pages of tables. However, we reduced these 600 complicated data structures to one unique and simple event model.
    By means of shifting clinical data from the old type order entry system into the new order entry system of the medical information event model, we produced a simple and flexible system, and the easy secondary use of clinical data of patients was realized. Evaluation of our system revealed heightened data retrieval efficiency and shortened response time 1: 600 at a terminal, owing to the 1: 600 reduction of the number of tables as mentioned above.
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