Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 69, Issue 12
Displaying 1-13 of 13 articles from this issue
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Opening Article
Originals
  • Evaluation of a Risk Communication Approach for Maintenance Staff Working with Induced Radioactivity in Medical Linear Accelerators
    Hiroshi Watanabe,, Ichiro Yamaguchi, Yoshiaki Maehara, Mitsue Koizumi, ...
    2013 Volume 69 Issue 12 Pages 1353-1362
    Published: December 20, 2013
    Released on J-STAGE: December 20, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.12.1353
    JOURNAL FREE ACCESS
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    In order to promote consensus building on decommissioning operation rules for medical linear accelerators in Japan, we carried out a risk communication (RC) approach mainly providing knowledge for maintenance staff regarding induced radioactivity. In February 2012, we created a booklet (26 pages) to present an overview of the amended law, the mechanism and the distribution of induced radioactivity showing the actual radiation dose rate around a linear accelerator and actual exposure doses to staff. In addition, we co-sponsored a seminar for workers in this field organized by the Japan Medical Imaging and Radiological Systems Industries Association to explain the contents of this booklet, and answer questions regarding induced radioactivity of linear accelerators as an RC program. As a result, the understanding of staff regarding the regulations on maximum X-ray energy on linear accelerators (P<0.05), and the outline of clearance systems (P<0.01), were facilitated by RC. In addition, we found that about 70% of maintenance staff considered that the cooling time for decommissioning operation depended on the situation. Our RC approach suggests that consensus building should be used to make rules on decommissioning operations for linear medical accelerators.
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  • Bilateral Filter Applied to Bone Scintigraphy
    Yutaka Katayama, Kentaro Ueda, Shinsaku Hiura, Takashi Yamanaga, Hisan ...
    2013 Volume 69 Issue 12 Pages 1363-1371
    Published: December 20, 2013
    Released on J-STAGE: December 20, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.12.1363
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    The aim of this study is to improve the image quality using a post process rather than a correction process at acquisition time. We used a smoothing filter that is widely used on a compact digital camera. Especially for nuclear medicine, when we use a short acquisition time, we will get images that have a large increase in statistical noise. For those images, we validated the efficiency of the smoothing filter by assessing two characteristic parameters. In addition, we defined the best smoothing filter parameters to get stable images that reduced the influence of statistical noise.
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  • Dose Estimation for Exposure Conditions of Diagnostic Radiology Acquired by a 2011 Questionnaire in a Phantom Study
    Yuta Matsunaga, Ai Kawaguchi, Kenichi Kobayashi, Yasuki Asada, Yukinor ...
    2013 Volume 69 Issue 12 Pages 1372-1378
    Published: December 20, 2013
    Released on J-STAGE: December 20, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.12.1372
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    Using a 2011 questionnaire, the Japanese Society of Radiological Technology conducted a nationwide survey on the exposure conditions in diagnostic radiography. The purpose of this study was to measure the entrance surface dose and absorbed dose for each organ dose and to calculate the effective dose using a human phantom with the 2011 exposure conditions. We estimated the patient exposure doses during skull (antero-posterior), chest (postero-anterior), abdomen (antero-posterior), and lumbar vertebrae (antero-posterior, left-right, and right-left) radiographs. The radiation doses were determined by placing 255 thermoluminescence dosimeters at various positions on and in the phantom, including the surface of the skin, head, thyroid, lung, breast, esophagus, stomach, liver, and gonads. The maximum entrance surface dose was 7.83 mGy, which occurred to the lateral lumbar spine. In addition, the minimum entrance surface dose was 0.24 mGy, to the chest. The maximum organ dose was 3.15 mGy, to the stomach of the lateral lumbar vertebrae (LR). Meanwhile, the maximum effective dose was 0.63 mSv, to the lateral lumbar vertebrae (LR). On the contrary, the minimum effective dose was 0.03 mSv, to the head. We could evaluate the entrance surface dose, absorbed dose for each organ dose, and effective doses using the 2011 exposure conditions in Japan. The entrance surface dose of 5 examinations with these exposure conditions was below the guidance level of the IAEA. In the future, it can be said that the entrance surface dose as well as the effective dose require diagnostic reference levels in radiography.
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  • Quality Control of Dose Calibrator Using a Traceable Syringe-type 68Ge/68Ga Calibration Source
    Noriaki Miyaji, Kenta Miwa, Kei Wagatsuma, Takuro Umeda, Taisuke Murat ...
    2013 Volume 69 Issue 12 Pages 1379-1386
    Published: December 20, 2013
    Released on J-STAGE: December 20, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.12.1379
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    Objectives: Accurate calibration of dose calibrators (DC) is required for quantitative positron emission tomography (PET) studies to generate meaningful information. Values measured by DC depend not only on the radioactive nuclide but also the environment where measurements are taken. Therefore, DC must be calibrated at each location. The present study aimed to determine appropriate calibration values, and evaluate the performance of DC using a traceable 68Ge/68Ga calibration source that is available as a surrogate 18F source. Methods: We used a 68Ge/68Ga calibration source to determine the optimal DC value for measuring 18F activity in the operating environment. Variations in sensitivity and geometry as well as measurement uncertainty were evaluated using the 68Ge/68Ga source. We adopted the criteria of the Guide for the expression of uncertainty in measurement (GUM) to evaluate DC performance. Results: Although the manufacturer’s recommended 18F calibration number for the CRC-25PET is 480, we found that the optimal number was 482. Over a period of one year, the sensitivity of the DC varied <0.1%, and the expanded uncertainty of DC measurements was 2.2%. Conclusion: Measurements of the certified activity of a traceable national standard were corrected, and the uncertainty of measurements as well as the accuracy of a DC were determined. Calibration numbers for DC should be regularly determined using 68Ge/68Ga calibration sources at each location to ensure the most accurate results.
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  • Presumption of the Energy-spectrum of High-energy Electron Beam Based on the Beta-distribution Model
    Hideki Kato, Naoki Hayashi, Ryohei Kuroki, Yumiko Adachi, Shizuma Suzu ...
    2013 Volume 69 Issue 12 Pages 1387-1393
    Published: December 20, 2013
    Released on J-STAGE: December 20, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.12.1387
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    The energy spectra of high-energy electron beams used in radiotherapy are the most important data for evaluating absorbed doses and/or dose distributions in the body of a patient. However, it is impossible to measure the actual spectra of a high-energy electron beam. In this study, we suggest a method to presume the spectra of high-energy electron beams by use of the beta distribution model. The procedure of this method is as follows: (1) the spectrum of the high-energy electron beam was assumed to have a maximum energy Emax, and α, β parameters of the beta probability density function. (2) The percentage depth dose (PDD) based on the assumed spectrum was calculated by a Monte Carlo simulation. (3) The best matching energy spectrum was searched in comparison with the experimental PDD curves. Finally, the optimal energy spectrum of the electron beam was estimated after reiterating the process from (1) to (3). With our method, the measured PDD curves were optimally simulated following the experimental data. It appeared that the assumed spectra approximated well to the actual spectra. However, the error between the assumed and experimental data was observed in the region under the incident surface. We believe this was due to the influence of low-energy electrons scattered at installed collimators, etc. In order to simulate PDDs in this region accurately, a further correction process is required for a spectrum based on the beta distribution model.
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Clinical Technologies
  • Basic Evaluation of the Optimal Flip Angle for Hepatocyte Phase with Gadolinium Ethoxybenzyl Diethylenetriamine Pantaacetic Acid: Selection of the Optimal Flip Angle by the Imaging Findings
    Daisuke Oura, Kyouhei Abe, Toshikazu Nambu, Yoshihiro Kondo
    2013 Volume 69 Issue 12 Pages 1394-1404
    Published: December 20, 2013
    Released on J-STAGE: December 20, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.12.1394
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    Gadolinium ethoxybenzyl diethylenetriamine pantaacetic acid (Gd-EOB-DTPA) is incorporated into liver cells, and liver parenchyma show hyperintensity due to the T1 shortening effect. The T1 value of liver parenchyma in the hepatocyte phase changes from the pre-contrast phase. However, in patients with liver dysfunction, the difference of T1 value is generally small. In examination of hepatic disease, the optimal flip angle should be selected according to the patient’s state. The definition of hepatic dysfunction based on biochemical data is diverse. Therefore, if the image findings can estimate liver dysfunction, the operator will select the optimal flip angle. Hence, we defined the criteria of liver dysfunction based on the image data; one or more of the following abnormalities-irregular liver surface, splenomegaly, and expansion of portal trunk. In classification by imaging data, we compared the T1 value of liver parenchyma in the hepatocyte phase, and found that the T1 value was significantly different between normal and cirrhotic liver. Then, in a phantom study simulating normal and cirrhotic liver, we set the optimal flip angle (FA)-21 degrees for the normal liver state, and 18 degrees for the LC state. In Gd-EOB-DTPA-enhanced study, the operator can select the optimal FA for each patient according to the image findings.
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  • Development of Quality Assurance/Quality Control Web System in Radiotherapy
    Hiroyuki Okamoto, Toshihiko Mochizuki, Kazutoshi Yokoyama, Akihisa Wak ...
    2013 Volume 69 Issue 12 Pages 1405-1411
    Published: December 20, 2013
    Released on J-STAGE: December 20, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.12.1405
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    Our purpose is to develop a QA/QC (quality assurance/quality control) web system using a server-side script language such as HTML (HyperText Markup Language) and PHP (Hypertext Preprocessor), which can be useful as a tool to share information about QA/QC in radiotherapy. The system proposed in this study can be easily built in one’s own institute, because HTML can be easily handled. There are two desired functions in a QA/QC web system: (i) To review the results of QA/QC for a radiotherapy machine, manuals, and reports necessary for routinely performing radiotherapy through this system. By disclosing the results, transparency can be maintained, (ii) To reveal a protocol for QA/QC in one’s own institute using pictures and movies relating to QA/QC for simplicity’s sake, which can also be used as an educational tool for junior radiation technologists and medical physicists. By using this system, not only administrators, but also all staff involved in radiotherapy, can obtain information about the conditions and accuracy of treatment machines through the QA/QC web system.
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Data
  • The Survey of Radiation Dose in Radiofrequency Catheter Ablation
    Takao Kanzaki, Masashi Andou, Hiroki Okada, Syo Nakamura, Hiroyuki Tak ...
    2013 Volume 69 Issue 12 Pages 1412-1417
    Published: December 20, 2013
    Released on J-STAGE: December 20, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.12.1412
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    Interventional radiology (IVR) is a technique using image guidance such as X-ray fluoroscopy to perform diagnostic and therapeutic procedures. It is widespread, and its use continues to increase. Radiofrequency catheter ablation (RFCA) has a long fluoroscopy time, and ablation procedures may be repeated in a single session. The entrance skin dose may reach several Gy, but information on radiation dose of actual procedures is limited. We conducted a survey on RFCA to acquire general information on how the procedures are performed in local institutions, including patient radiation dose in the Kanto area. 43% (33/77 institutions) of institutions to which we sent written questionnaires returned completed forms. Ablation for atrial fibrillation had the longest average fluoroscopy times (100.8 min) and average procedure times (228 min), and average air kerma at the interventional reference point (1173.6 mGy). Percutaneous coronary intervention and RFCA may cause skin injury, which suggests the continued need for radiation safety management.
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The 69th Annual Scientific Congress
Educational Lecture—Statistical Methods for Radiologic Research
Basic Lecture—Heart Disease: From Diagnosis to Treatment
JIRA Topics
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