Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 66, Issue 5
Displaying 1-15 of 15 articles from this issue
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Opening Article
Originals
  • Measurement of Effective Energy and Entrance Surface Dose Using Fluorescent Glass Dosimeter in Interventional Radiology Procedures: Make of Half-value Layer Measurement Instrument and IVR-Phantom
    Hiroji Iida, Kimiya Noto, Tadanori Takata, Mitsuhiro Chabatake,, Tomoy ...
    2010 Volume 66 Issue 5 Pages 487-494
    Published: November 25, 2009
    Released on J-STAGE: July 09, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.487
    JOURNAL FREE ACCESS
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    In interventional radiology (IVR) procedures, automatic brightness control (ABC) is helpful in maintaining good image quality by adjusting kV and/or mA based on the subject’s thickness. However, it was difficult to measure effective energy using half-value layer (HVL). We investigated the usefulness of measuring effective energy and entrance surface dose using a fluorescent glass dosimeter in IVR procedures, and we made an HVL folder and IVR-phantom for that purpose. Effective energy measured using the HVL folder correlated well with reference ionization dosimeter (y=0.992x, r=0.963). The result indicated that the present method using an HVL folder and IVR-phantom provides accurate measurements of effective energy and entrance surface dose in IVR procedures. In conclusion, the present measurement method may be useful for quality control of IVR equipment. In addition, the development of this measurement technique may be useful for comparisons of exposure levels in different hospitals.
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  • Analysis of Photonuclear Activation Effect of High-energy Medical Linear Accelerators — Measurement of Spatial Dose Distribution and Temporal Decay Curve, and Assessment of Personnel Dosimetry
    Hiroshi Fukuma, Yuta Eguchi, Shigeru Isoyama, Makoto Kawano, Yusuke Su ...
    2010 Volume 66 Issue 5 Pages 495-501
    Published: November 25, 2009
    Released on J-STAGE: July 09, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.495
    JOURNAL FREE ACCESS
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    The characteristics of activation after high-energy X-rays have been generated by medical linear accelerators were measured using an ionization chamber. Radiation doses increased with rising X-ray energy, based on 10 MV, 15 MV, and 18 MVX-ray measurements. When the total irradiation dose was changed, radiation dose increased with total irradiation dose. When the collimator opened, the radiation dose at a position 15 cm from the isocenter reached about the maximum, which was 2.2 times the dose at the isocenter. The radiation dose became about 0.3 times its level at a position 40 cm from the isocenter, in the outer irradiation field. The dose distribution in the treatment room became almost the same dose extending from the isocenter to 200 cm. Radiation dose decreased gradually while moving away from the target on the treatment beam axis. But it increased again as it approached the floor face. The occupational exposure dose, which was presumed from measurements of the radiation dose 50 cm from the isocenter, was about 0.9 mSv during a year, assuming 600 MU for 1 person, 8 people a day, and 245 days a year. Radiation dose changed with X-ray energy in the machine used, and it was a geometrical constituent in the treatment room. It is important to understand the characteristics of radiation generated by medical linear accelerators.
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Notes
  • Quantitative Evaluation of Gd-EOB-DTPA Uptake in Phantom Study for Liver MRI
    Norio Hayashi, Tosiaki Miyati, Wataru Koda, Masayuki Suzuki, Shigeru S ...
    2010 Volume 66 Issue 5 Pages 502-508
    Published: November 25, 2009
    Released on J-STAGE: July 09, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.502
    JOURNAL FREE ACCESS
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    Gd-EOB-DTPA is a new liver specific MRI contrast media. In the hepatobiliary phase, contrast media is trapped in normal liver tissue, a normal liver shows high intensity, tumor/liver contrast becomes high, and diagnostic ability improves. In order to indicate the degree of uptake of the contrast media, the enhancement ratio (ER) is calculated. The ER is obtained by calculating (signal intensity (SI) after injection-SI before injection) / SI before injection. However, because there is no linearity between contrast media concentration and SI, ER is not correctly estimated by this method. We discuss a method of measuring ER based on SI and T1 values using the phantom. We used a column phantom, with an internal diameter of 3 cm, that was filled with Gd-EOB-DTPA diluted solution. Moreover, measurement of the T1 value by the IR method was also performed. The ER measuring method of this technique consists of the following three components: 1) Measurement of ER based on differences in 1/T1 values using the variable flip angle (FA) method, 2) Measurement of differences in SI, and 3) Measurement of differences in 1/T1 values using the IR method. ER values calculated by these three methods were compared. In measurement made using the variable FA method and the IR method, linearity was found between contrast media concentration and ER. On the other hand, linearity was not found between contrast media concentration and SI. For calculation of ER using Gd-EOB-DTPA, a more correct ER is obtained by measuring the T1 value using the variable FA method.
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  • Energy Characteristics and Examination of the Dose Correction of Each Element Type in Small Size Radiophotoluminescence Glass Dosimetry Element System
    Shogo Harui, Mitsuhiro Matsumoto, Yuji Ogata
    2010 Volume 66 Issue 5 Pages 509-514
    Published: November 25, 2009
    Released on J-STAGE: July 09, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.509
    JOURNAL FREE ACCESS
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    We studied energy characteristics and examined dose correction when using a radiophotoluminescence glass dosimeter (GD). There are two types of GD. One type of GD is called GD-352, which consists of a glass element and Sn filter. Another type of GD is called GD-302, which has no additional filter. Energy characteristics of these two types of GDs were investigated using a diagnostic X-ray energy range. The equation is as follows: Cf (correction factor) = average of GD measured value/air kerma. The compensation formula for estimating air kerma with each X-ray energy was determined from an approximation formula based on the ratio between GD system reading and air kerma with a specific X-ray energy. From compensation results obtained using the formula, the error for air kerma using GD-352 was approximately 0%, and the error using GD-302 was about 1.0%.
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Clinical Technology
  • Radiation Dose Reduction Using a Non-Linear Image Filter in MDCT
    Junya Nakashima, Toshiyuki Takahashi, Yoshimasa Takahashi, Yasuhiro Im ...
    2010 Volume 66 Issue 5 Pages 515-524
    Published: November 25, 2009
    Released on J-STAGE: July 09, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.515
    JOURNAL FREE ACCESS
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    The development of MDCT enabled various high-quality 3D imaging and optimized scan timing with contrast injection in a multi-phase dynamic study. Since radiation dose tends to increase to yield such high-quality images, we have to make an effort to reduce radiation dose. A non-linear image filter (Neuro 3D filter: N3D filter) has been developed in order to improve image noise. The purpose of this study was to evaluate the physical performance and effectiveness of this non-linear image filter using phantoms, and show how we can reduce radiation dose in clinical use of this filter. This N3D filter reduced radiation dose by about 50%, with minimum deterioration of spatial reduction in phantom and clinical studies. This filter shows great potential for clinical application.
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  • Comparison of Dose Distribution on Radiographic Film and Radiochromic Film for Intensity Modulated Radiation Therapy
    Motoharu Sasaki, Masahide Tominaga, Hitoshi Ikushima, Taro Kishi, Tets ...
    2010 Volume 66 Issue 5 Pages 525-534
    Published: November 25, 2009
    Released on J-STAGE: July 09, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.525
    JOURNAL FREE ACCESS
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    Purpose: Radiographic film is generally used for inspection of dose distribution in intensity modulated radiation therapy (IMRT) at many institutions. However, the distribution of filmless systems can be expected to be used increasingly in the future. Therefore, we confirmed the utility of radiochromic film by comparing it with radiographic film that does not need an automatic processor. Result: Difference in does measured by radiographic film and radiochromic film tended to increase in the low does area, but it was limited in a range of 1.5%. Conclusion: When the dose distribution was verified in a highly accurate radiation therapy such as IMRT, the results suggested that radiochromic film can be useful in addition to radiographic film.
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Work in Progress
  • Visualization of Laryngopharynx during Swallowing of Negative Contrast Media (Air) with Cine Mode 64-row MDCT
    Taku Fudeya, Shoichiro Otake, Hirotaka Watabe, Takashi Mitsuoka, Akito ...
    2010 Volume 66 Issue 5 Pages 535-540
    Published: November 25, 2009
    Released on J-STAGE: July 09, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.535
    JOURNAL FREE ACCESS
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    Video fluoroscopic examination of swallowing generally needs a contrast media such as a barium sulfate. Since the examination is usually performed in patients with dysphasia, there is a risk of aspiration. We tried to visualize the laryngopharynx during swallowing of negative contrast media (air) with 64-row multi-detector computed tomography (64-MDCT). Cine mode 64-MDCT was performed to visualize the laryngopharynx in 4 healthy volunteers during swallowing of negative contrast media (air). The data were converted to three-dimensional (3D) images of 2 conditions (air and bone) and sagittal images of the soft tissue condition at a workstation. These images were sent to a personal computer and modeled to 3D cine images with Digital Imaging and Communication in Medicine (DICOM) Viewer and Quick Time Player. 3D cine images demonstrated movements of the epiglottis, vallecula, piriform sinus, tongue, pharyngeal wall, hyoid bone and thyroid cartilage.
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The 64th Annual Scientific Congress
Educational Lecture-Basic Thinking of Image Analysis
Educational Lecture-Research Methodology
Basic Lecture-How to Make Use of Softwares
Clinical Technology Course
Report from the Scientific Research Group
JIRA Topics
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