Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 69, Issue 4
Displaying 1-17 of 17 articles from this issue
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Opening Article
Originals
  • Investigation of Patient Exposure Doses in Diagnostic Radiography in 2011 Questionnaire
    Yasuki Asada, Syoichi Suzuki, Kenichi Kobayashi, Hideyuki Kato, Takayu ...
    2013 Volume 69 Issue 4 Pages 371-379
    Published: April 20, 2013
    Released on J-STAGE: April 22, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.4.371
    JOURNAL FREE ACCESS
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    We report here the results of a dose evaluation based on information obtained in a 2011 questionnaire as compared with an investigation made in 2007. Briefly, in general radiography, the dose used in most examinations in 2011 was lower than in 2007. However, since the entrance surface dose for chest X-rays showed an increase, there is a need to standardize the taking of digital images to be able to decrease the dose. Although computed tomography dose index volume (CTDIvol) in CT examinations was higher than that revealed in the 2007 investigation, there is potential for dose reduction.
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  • Optimization of High Flip Angle for Late Gadolinium Enhancement Magnetic Resonance Imaging by Phase-Sensitive Inversion Recovery Sequence
    Satoshi Yoshizawa, Toshio Tsuchihashi, Satoshi Harashina, Akira Yoshim ...
    2013 Volume 69 Issue 4 Pages 380-385
    Published: April 20, 2013
    Released on J-STAGE: April 22, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.4.380
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    This study focuses on optimization of the flip angle (FA) of phase-sensitive inversion recovery (PSIR) reconstruction (PSIR-FA) to achieve improved tissue contrast. Intensity normalization removes the larger variations in image intensity caused by falloff, thus improving the visualization of tissue contrast. We evaluated tissue contrast for images in healthy volunteers using the phantom influence of T1 relaxation and FA. T1 relaxation is improved due to the T1* effect and enables a high PSIR-FA to be set. The contrast-to-noise ratio (CNR) of the PSIR-FA 20° image is good, since magnetization is almost fully restored to normal. The usefulness of PSIR-FA 20 images was proved statistically. PSIR-FA 20° shows improved tissue contrast as a result of the high accuracy of intensity normalization.
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Notes
  • Proposal of a Cloud Chamber Experiment Using Diagnostic X-ray Apparatus and an Analysis Assisted by a Simulation Code
    Hiroaki Hayashi, Hiroki Hanamitsu, Sadamitsu Nishihara, Junji Ueno, Hi ...
    2013 Volume 69 Issue 4 Pages 386-392
    Published: April 20, 2013
    Released on J-STAGE: April 22, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.4.386
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    A cloud chamber is a radiation detector that can visualize the tracks of charged particles. In this study, we developed a middle-type cloud chamber for use in practical training using a diagnostic X-ray apparatus. Because our cloud chamber has a heater to vaporize ethanol and features antifogging glass, it is possible to observe the vapor trails for a long time without the need for fine adjustments. X-rays with a tube voltage of 40 kV or of 120 kV (with a 21-mm aluminum filter) were irradiated at the chamber and the various phenomena were observed. We explain these phenomena in terms of the range of electrons and/or interactions between X-rays and matter and conclude that our analysis is consistent with analysis using the Monte Carlo simulation code EGS5.
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  • Observations of Deterioration of Photo-Stimulable Phosphor Plates Used in Digital Mammography and Its Effects on Mammography Diagnoses
    Mitsuyoshi Yasuda, Kyoichi Kato, Syun Kurosawa, Kohki Yoshikawa, Hisay ...
    2013 Volume 69 Issue 4 Pages 393-399
    Published: April 20, 2013
    Released on J-STAGE: April 22, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.4.393
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    We noted that breast-like artifacts occur in photo-stimulable phosphor plates (PSPs) used for long periods in digital mammography systems. This prompted us to investigate the effects on mammography diagnoses of these artifacts. Our study took the form of a comparison between the images generated by a long-term use PSP (four years use) and a short-term use PSP. First, an acrylic phantom and an in-house-made phantom for visual evaluation were imaged using X-ray PSPs under the same exposure conditions. They were then scanned under the same conditions to generate images. The mean values of the digital signals were measured in the 35 locations of region of interest present in the images of the acrylic phantom. The images of the in-house-made phantom were then visually evaluated by five certified experts, who examined 22 clinical images taken with both PSPs while referring to a visual evaluation scale. Differences were detected in all the evaluated items: the short-term use PSP gave a higher rate than the long-term use PSP (p<0.01), suggesting that long-term use PSPs might adversely affect the results of diagnostic mammography.
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Clinical Technologies
  • Dose Impact of a Carbon Fiber Couch for Stereotactic Body Radiation Therapy of Lung Tumors
    Hirofumi Tominaga, Fujio Araki, Yoshinobu Shimohigashi, Nagisa Kanetak ...
    2013 Volume 69 Issue 4 Pages 400-406
    Published: April 20, 2013
    Released on J-STAGE: April 22, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.4.400
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    The aim of this study was to measure the dose attenuation caused by a carbon fiber radiation therapy table (Imaging Couch Top; ICT, BrainLab) and to evaluate the dosimetric impact of ICT during stereotactic body radiation therapy (SBRT) in lung tumors. The dose attenuation of ICT was measured using an ionization chamber and modeled by means of a treatment planning system (TPS). SBRT was planned with and without ICT in a lung tumor phantom and ten cases of clinical lung tumors. The results were analyzed from isocenter doses and a dose-volume histogram (DVH): D95, Dmean, V20, V5, homogeneity index (HI), and conformity index (CI). The dose attenuation of the ICT modeled with TPS agreed to within ±1% of the actually measured values. The isocenter doses, D95 and Dmean with and without ICT showed differences of 4.1–5% for posterior single field and three fields in the phantom study, and differences of 0.6–2.4% for five fields and rotation in the phantom study and six fields in ten clinical cases. The dose impact of ICT was not significant for five or more fields in SBRT. It is thus possible to reduce the dose effect of ICT by modifying the beam angle and beam weight in the treatment plan.
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  • Optimal Scan Parameters for a Method of k-space Trajectory (Radial Scan Method) in Evaluation of Carotid Plaque Characteristics
    Manami Nakamura, Takeshi Makabe, Hideomi Tezuka, Takahiro Miura, Takum ...
    2013 Volume 69 Issue 4 Pages 407-412
    Published: April 20, 2013
    Released on J-STAGE: April 22, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.4.407
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    The purpose of this study was to optimize scan parameters for evaluation of carotid plaque characteristics by k-space trajectory (radial scan method), using a custom-made carotid plaque phantom. The phantom was composed of simulated sternocleidomastoid muscle and four types of carotid plaque. The effect of chemical shift artifact was compared using T1 weighted images (T1WI) of the phantom obtained with and without fat suppression, and using two types of k-space trajectory (the radial scan method and the Cartesian method). The ratio of signal intensity of simulated sternocleidomastoid muscle to the signal intensity of hematoma, blood (including heparin), lard, and mayonnaise was compared among various repetition times (TR) using T1WI and T2 weighted imaging (T2WI). In terms of chemical shift artifacts, image quality was improved using fat suppression for both the radial scan and Cartesian methods. In terms of signal ratio, the highest values were obtained for the radial scan method with TR of 500 ms for T1WI, and TR of 3000 ms for T2WI. For evaluation of carotid plaque characteristics using the radial scan method, chemical shift artifacts were reduced with fat suppression. Signal ratio was improved by optimizing the TR settings for T1WI and T2WI. These results suggest the potential for using magnetic resonance imaging for detailed evaluation of carotid plaque.
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  • A New Radiographic Technique for Detecting Avulsion Fracture of the Lateral Malleolus in Children
    Kazuyoshi Nanba, Satoshi Nakanishi, Tsuyoshi Yamada, Morihiro Ito
    2013 Volume 69 Issue 4 Pages 413-418
    Published: April 20, 2013
    Released on J-STAGE: April 22, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.4.413
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    The objectives of this study were to determine the usefulness of a newly-developed distal fibular axial view radiography modified method for depicting avulsion fracture of the lateral malleolus in children from a functional anatomy viewpoint. Conventional radiography was applied to sixty-nine avulsion fracture suspected ankles of 67 children. Average age and standard deviation at injury were 8.00 and 1.46, respectively. We compared the ability of the modified method to detect avulsion fractures of the lateral malleolus with those could not be depicted using the conventional method, and noted that 42 avulsion fractures (60.9%) could be depicted using the conventional method. We applied the modified method to 27 joints that the conventional method had diagnosed as normal. Of these, the modified method detected 13 avulsion fractures (48.1%). In conclusion, the modified radiography method made it possible to depict avulsion fracture of the lateral malleolus in cases that resisted detection by the conventional method.
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  • Study of Optimal Flip Angle for Inversion-recovery Gradient Echo Method in Delayed Contrast-enhanced Cardiac Magnetic Resonance Imaging
    Masashi Ogawa, Yoshio Matsumura, Toshio Tsuchihashi
    2013 Volume 69 Issue 4 Pages 419-425
    Published: April 20, 2013
    Released on J-STAGE: April 22, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.4.419
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    Delayed contrast-enhanced cardiac magnetic resonance imaging (MRI) is a valuable tool for detecting myocardial infarction and assessing myocardial viability. The standard viability MRI technique is the inversion-recovery gradient echo (IR-GRE) method. Several previous studies have demonstrated that this imaging technique provides superior image quality at high magnetic field strengths, e.g., 3.0 T. However, there are numerous possible flip angles. We investigated the optimal flip angle of IR-GRE in delayed contrast-enhanced cardiac MRI. Phantoms were made that modeled infarcted myocardium and normal myocardium after administration of contrast agent. To determine optimal flip angle, we compared the contrast-to-noise ratio (CNR) among these phantoms and evaluated the degree of artifacts induced by increased flip angle. The flip angle that showed the highest CNR for 2D IR-GRE and 3D IR-GRE was 30°/15° at 1.5 T and 25°/15° at 3.0 T. The flip angle that showed the highest CNR was independent of R-R interval. Streak artifacts induced by increased flip angle tended to occur more readily at 3.0 T than 1.5 T. The optimal flip angle for 2D IR-GRE and 3D IR-GRE at 1.5 T was 30° and 15°, respectively. At 3.0 T, taking into account the results for both CNR and streak artifacts, we concluded the optimal flip angle of 2D IR-GRE to be 15–20°.
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The 40th Autumn Scientific Congress
Educational Lecture–Statistical Methods for Radiologic Research
Basic Lecture–From Diagnosis of the Breast to Treatment
Basic Lecture–Three-dimensional Computer Graphics
Clinical Technology Course
Science Exchanges Committee Report
JIRA Topics
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