Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
Volume 64 , Issue 1
Showing 1-16 articles out of 16 articles from the selected issue
Opening Article
New Year Round Table Discussion
Originals
  • Shoji Tani, Chiharu Tanabe, Shuji Abe, Kazuhiro Mihara
    2008 Volume 64 Issue 1 Pages 15-24
    Published: January 20, 2008
    Released: March 01, 2008
    JOURNALS FREE ACCESS
    We devised an application that uses the “Maximum value reading method (AutoIV)” for bedside chest radiography in a neonatal intensive care unit (NICU) that used the Fuji Computed Radiography (FCR) System. The application, named AutoIV-N, uses the relationship for density correction between radiographic conditions (mAs) and the Display Parameter (GS). GS=f (mAs) can be considered the relationship that connects FCR and the X-ray generator. When AutoIV-N is used, radiographic image contrast does not change. Further, radiographic image density fluctuation can be eliminated by random elements such as X-ray output fluctuation of the X-ray generator and the decline of photo-stimulated luminescence caused by fading of the imaging plate. Accordingly, image recording that is suitable for follow-up chest radiography is made possible. We choose nine patients and performed a comparison of radiographic density fluctuation in AutoIV-N and Fix. AutoIV-N was found to be more stable than Fix. It is possible to use the radiographic imaging condition that is optimized for all patients in the NICU by AutoIV-N. This facilitates radiation exposure optimization in medicine. (Article in Japanese)
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  • Toshinori Maruyama, Hideki Yamamoto
    2008 Volume 64 Issue 1 Pages 25-34
    Published: January 20, 2008
    Released: March 01, 2008
    JOURNALS FREE ACCESS
    A good positioning technique is of great importance in radiology in order to obtain accurate diagnostic information and reduce the patient’s X-ray exposure. In positioning training, students place the phantom on the table under an X-ray tube, adjust the position of the phantom, and repeat the positioning practices until they can obtain fine diagnostic images. As X-ray films are usually used in radiography, the development of such films is necessary. In this kind of training practice, it takes a great deal of time to obtain the X-ray image at the phantom position. It is desirable for students to perform positioning accurately and to confirm the results of positioning within a short time. In this article, we propose a new positioning training method using digital image processing. First, we scan the skull phantom by CT (computed tomography) and obtain CT images. Next, we measure the positioning information of the phantom under the X-ray equipment by using scene analysis. Then, we develop a method that produces the plane image corresponding to the detected phantom position under the X-ray tube. It is expected that our method will be useful as a teaching device to help in the practice of the positioning techniques for various organs without X-ray exposure and, furthermore, in the development of X-ray films. (Article in Japanese)
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  • Toru Takakura, Kana Matsubara, Takashi Mizowaki, Manabu Nakata, Shinsu ...
    2008 Volume 64 Issue 1 Pages 35-40
    Published: January 20, 2008
    Released: March 01, 2008
    JOURNALS FREE ACCESS
    Background and Purpose: We verified the propriety of our systematic error reduction strategy by means of a computer simulation based on our data of position error with a prone fixation device for prostate IMRT. Materials and Methods: Computer simulations of the off-line correction method for systematic setup errors based on the portal imaging taken on the first several days of the treatment session were performed. Using the computer simulations, an optimal number of portal images were evaluated for the SD value, from 0.5 mm to 1.5 mm at a 0.25 mm interval, and the respective required setup margins were calculated. Results: The value of systematic error was reduced as the frequency of data obtained increased. Moreover, the reduction rate was so remarkable that random error was large. (Article in Japanese)
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  • Shinji Sakai, Reiji Katayama, Junji Morishita, Taro Sakaguchi, Seiji O ...
    2008 Volume 64 Issue 1 Pages 41-49
    Published: January 20, 2008
    Released: March 01, 2008
    JOURNALS FREE ACCESS
    The purpose of this study was to evaluate the basic imaging properties of the two latest digital radiographic X-ray systems, namely, the DynaDirect Winscope 6000 (abbr. as System A, Toshiba Medical Systems) and the Sonialvision Safire Multi (abbr. as System B, Shimadzu Corp.). These systems were based on a direct-conversion flat panel detector (FPD) of amorphous selenium. The basic imaging properties of the two systems were evaluated by measuring characteristic curves, presampled modulation transfer functions (MTFs), and noise power spectra (NPS) using DICOM images to which no resampling was performed with a matrix size of 2048×2048. In addition, noise equivalent quanta (NEQ) and detective quantum efficiency (DQE) calculated from the result of the basic imaging properties were evaluated. The characteristic curves of the two systems showed quite high linearity. The MTFs of the two systems indicated high-resolution properties, as is well known to be an advantage of the direct conversion FPD system. However, the NPS of System A showed better performance than System B under the same exposures. Therefore, the DQE of System A was higher than that of System B at all spatial frequencies. (Article in Japanese)
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  • Takanori Hara, Katsuhiro Ichikawa, Shinji Niwa
    2008 Volume 64 Issue 1 Pages 50-56
    Published: January 20, 2008
    Released: March 01, 2008
    JOURNALS FREE ACCESS
    Analysis of the detailed physical property in CT system is important in an understanding of a clinical image. In this study, we evaluated resolution power property about the positions and direction for in-plane in CT system. The indexes of the resolving power property of CT images were measured by MTFs using the thin metal wire (diameter of 0.2 mm). We measured the positions of the iso-center and the off-center (32 mm, 64 mm, 96 mm, 128 mm) in in-plane. One-dimensional MTFs for the X-direction and Y-direction were calculated by the numerical slit scanning method. Then, MTF was calculated from the corresponding direction. As a result, when a filter kernel of high resolutions (B70) is used in the position of 128 mm, the resolution of X-direction was inferior to the Y-direction about 30% (at the MTF-value of 0.5 cycles/mm). Moreover, the resolution of X-direction at the position of 128 mm was inferior to the center about 33% (at the MTF-value of 0.5 cycles/mm). The resolving power property of in-plane in CT system was decreased in the calculation from the numerical slit that becomes perpendicular to the direction of centrifugal and, decreased proportionately with the distance from the center. Also, the resolutions along the centrifugal direction fell off remarkably at the peripheral area. And also, it turned out that the declining trend becomes larger, when the filter function for high-resolving power that is adapted for lungs is used. (Article in Japanese)
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Note
  • Yasuharu Wakabayashi, Kunihiko Morozumi, Masaki Shibasaki, Yukihiro Ma ...
    2008 Volume 64 Issue 1 Pages 57-64
    Published: January 20, 2008
    Released: March 01, 2008
    JOURNALS FREE ACCESS
    For ATP stress 99mTc-Tetrofosmin myocardial perfusion images (MPI), SPECT imaging is normally started 60 minutes after tracer injection. When the same procedure is applied to Adenosine (Ado) stress MPI, the frequency of the mask-out procedure after reconstruction (MOP) is increased. In this study, we examined the optimal imaging time from accumulation and distribution of isotope to neighboring organs. Time-count curves from dynamic and planer images of the heart, liver, and left upper abdomen were generated in 7 patients for optimal imaging time. MOP was evaluated in ATP stress MPI, in which imaging started 60 minutes after tracer injection (ATP 60), Ado stress MPI with imaging 60 minutes after injection (Ado 60), and Ado stress MPI with imaging 30 minutes after injection (Ado 30), in 575 patients. Up to 30 minutes after injection, washout from the liver was rapid, but after 30 minutes, it was slow. Washout from the left upper abdomen was not constant. MOP was 12.1% ATP 60, 23.1% Ado 60, and 13.2% Ado 30. Changing from Ado 60 to Ado 30 significantly decreased MOP (p<0.05). On adenosine stress MPI, it shortened examination time and enabled SPECT imaging to start 30 minutes after tracer injection. (Article in Japanese)
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Clinical Technology
  • Kosuke Matsubara, Kichiro Koshida, Masayuki Suzuki, Aya Nishimura, Hir ...
    2008 Volume 64 Issue 1 Pages 65-72
    Published: January 20, 2008
    Released: March 01, 2008
    JOURNALS FREE ACCESS
    In this study, we evaluated clinical images to determine appropriate settings for slice thickness in screening examinations for hepatocellular carcinoma and metastatic liver cancer, which are frequently performed in abdominal CT. The clinical images of 15 cases screened for hepatocellular carcinoma and 15 cases screened for metastatic liver cancer were evaluated. The evaluation was visually performed by three abdominal radiologists, and the sensitivity and specificity of each slice thickness were calculated. Results: differences in sensitivity and specificity were not found between slice thicknesses of 2.5 mm and 5.0 mm; however, sensitivity and specificity were low, and confidence was also low at a 10.0 mm slice thickness. Furthermore, when a 5.0 mm slice thickness was adopted, it was shown that radiation dose in limited parts could be reduced greatly to a noise level that compared equally with a study in which a 2.5 mm slice thickness was adopted in another evaluation. Therefore, the objective could be achieved by using a slice thickness of about 5.0 mm in multidetector-row CT examinations for the screening of liver cancer, while controlling patient dose to a minimum. (Article in Japanese)
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Educational Lecture—Interpreting Medical Images for Radiological Technologists
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