Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 69, Issue 1
Displaying 1-20 of 20 articles from this issue
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Opening Article
New Year Round Table Discussion
Originals
  • Electronic Portal Image Device Dosimetry for Volumetric Modulated Arc Therapy
    Daisaku Tatsumi, Ryosei Nakada, Akinori Ienaga, Akane Yomoda, Makoto I ...
    2013 Volume 69 Issue 1 Pages 11-18
    Published: January 20, 2013
    Released on J-STAGE: January 25, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.1.11
    JOURNAL FREE ACCESS
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    Recently electronic portal image devices (EPIDs) have been widely used for quality assurance and dose verification. However there are no reports describing EPID dosimetry for Elekta volumetric modulated arc therapy (VMAT). We have investigated EPID dosimetry during VMAT delivery using a commercial software EPIDose with an Elekta Synergy linac. Dose rate dependence and the linac system sag during gantry rotation were measured. Gamma indices were calculated between measured doses using an EPID and calculation made by a treatment planning system for prostate VMAT test plans. The results were also compared to gamma indices using films and a two-dimensional detector array, MapCHECK2. The pass rates of the gamma analysis with a criterion of 3% and 2 mm for the three methods were over 96% with good consistency. Our results have showed that EPID dosimetry is feasible for Elekta VMAT.
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  • Evaluation and Examination of Accuracy for the Conversion Factors of Effective Dose per Dose–Length Product
    Masanao Kobayashi, Tomoko Ootsuka, Syoichi Suzuki
    2013 Volume 69 Issue 1 Pages 19-27
    Published: January 20, 2013
    Released on J-STAGE: January 25, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.1.19
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    The purpose of this paper is to reappraise the accuracy of a conversion coefficient (k) reported by International Commission on Radiological Protection Publication 102 Table A.2. The effective doses of the routine head computed tomography (CT), the routine chest CT, the perfusion CT, and the coronary CT were evaluated using the conversion coefficient (adult head: 0.021 mSv·mGy－1·cm－1, adult chest: 0.014 mSv·mGy－1·cm－1). The dose length product (DLP) used the value displayed on the console on each scanning condition. The effective doses were evaluated using a human body type phantom (Alderson Rando phantom) and thermoluminescent dosimeter (TLD) elements for comparison with the converted value. This paper reported that the effective doses evaluated from conversion coefficient became different by 0.3 mSv (17%) compared with measurements, the effective dose computed with the conversion coefficient of the adult chest may be underestimated by 45%, and the bolus-tracking which scans the narrow beams should not use a conversion coefficient.
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  • Evaluation of Over Ranging in 64-slice Multidetector-row Computed Tomography Examinations for Upper Abdomen
    Hiroyuki Ueno, Kousuke Matsubara, Kichiro Koshida
    2013 Volume 69 Issue 1 Pages 28-32
    Published: January 20, 2013
    Released on J-STAGE: January 25, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.1.28
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    64-slice multidetector-row computed tomography (MDCT) have become widely used in recent years, but there is a possibility that a large volume of dose is radiated at the outside of the scope of scanning due to the effect of over ranging (OR). In this research, the dose volume change at the outside of the scope of scanning in the case of X-ray beam width (BW) and pitch factor (PF) is measured, and the effect of BW and PF on OR is considered. We scanned the upper abdomen of an acrylic human phantom using 64-slice multidetector-row CT in 4 conditions while changing BW and PF. We then measured the dose volume absorbed in the breasts, ovary, uterus, and the dose profile on the surface of phantom. As a result, when BW and PF are increased, the dose volume radiated at the outside of the scope of scanning increased, and the effect of OR appeared. Therefore, when BW and PF are set, X-ray radiated at the outside of the scope of scanning should also be considered.
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  • A Continuous 4-year Evaluation of Medical Informatics Education in a Graduate School of Health Sciences Using a Questionnaire Survey
    Satoru Monzen, Hideya Matsutani, Ikuo Kashiwakura
    2013 Volume 69 Issue 1 Pages 33-40
    Published: January 20, 2013
    Released on J-STAGE: January 25, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.1.33
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    The purpose of this study was to identify the level of awareness among undergraduate students regarding medical informatics and to ascertain whether educational training has progressed with time in the Department of Health Sciences at Hirosaki University, Japan, which is a co-medical staff training institution that conducts a 4-year university course in medical informatics. The university accepts students who have completed the 3rd grade of medical licensing tests and who have attended the medical informatics lectures for 4 years (2007–2010). The ratio of first sight terminology percentage in any given fiscal year in all the 30 terminology categories varied widely from 0% to 80%, but the trend in various categories did not vary between fiscal years. The terminology of informatics under medical technology students obtained high scores of 52.5–77.3% after attending courses, which was higher compared with students from other classes. On the other hand, student nurses and occupational therapy students obtained 0–44.2%. Each class scored a high percentage of correct answers in the medical information-related terminology. Among the radiology students who attended the classes, the percentage of correct answers in categories of “digital imaging and communication in medicine” and “picture archiving and communication system” were lower than other medical terminology categories. These results reflect the gaps in educational curriculum of 1st and 2nd grades of medical licensing tests.
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  • Usefulness of Top-hat Transform Processing in Whole Body Bone Scintigraphy
    Akinobu Kita, Katsuya Sugimoto, Tatsurou Tsuchida, Takahiro Kishimoto, ...
    2013 Volume 69 Issue 1 Pages 41-48
    Published: January 20, 2013
    Released on J-STAGE: January 25, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.1.41
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    To assess the usefulness of top-hat transform processing in whole body bone scintigraphy, five radiological technicians interpreted both original and top-hat processed images to determine the improvement of lesion detectability and interpretation time. For the evaluation of detectability, receiver operating characteristic (ROC) analysis was performed. The area under the curve (AUC) calculated from the ROC curve was improved in all observers (from 0.786 to 0.864 in average), although no significant difference was observed. However, the interpretation time was improved significantly (from 24.5 to 16.2 s in average). Top-hat transform processing in whole body bone scintigraphy is thought to be useful for the improvement of lesion detectability and interpretation time.
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  • Fundamental Evaluation of Wavelet Transform Based Noise Reduction Using Soft Threshold Method in Single Photon Emission Computed Tomography Image
    Norikazu Matsutomo, Hideo Onishi, Akio Nagaki, Akiyoshi Kinda
    2013 Volume 69 Issue 1 Pages 49-57
    Published: January 20, 2013
    Released on J-STAGE: January 25, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.1.49
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    Purpose: The wavelet transform is a newly developed signal-processing tool that decomposes a signal into various levels of resolution. The wavelet transform based noise reduction has the characteristics of optimally separating signal from noise, preserving the rapid rises and falls of a signal, and reconstructing a smooth signal from noise-imposed observations. The aim of this study was to evaluate the effects of applying a new noise reduction technique, the wavelet transform based noise reduction, to single photon emission computed tomography (SPECT) images. Methods: Three experiments were performed using cylindrical phantom, line source, and hot-rod phantom, respectively. We acquired SPECT image datasets of each phantom, and reconstructed SPECT images using the wavelet transform based noise reduction with filter back projection (FBP). Images were de-noised by 3 parameters of wavelet transform based noise reduction: 1st wavelet weight (WW), 2nd WW, and 3rd WW, respectively. We evaluated the variances of full width at half maximum (FWHM), coefficients of variation (%CV), and frequency domains (radius direction distribution function in the power spectrum), respectively. Results: In the cylindrical phantom test, %CV was reduced from 27.92% to 15.38% using the wavelet approach. On the other hand, FWHM values showed no significant change. However, the increases of wavelet weights caused artifacts on the reconstructed images in some cases. Conclusions: The wavelet based noise reduction had the significant potential to improve SPECT image. Therefore, the wavelet method should prove to be a robust approach to improve image quantification and fidelity.
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Note
  • Consideration of Algorithms to Presume the Lesion Location by Using X-ray Images of the Stomach—Geometric Analysis of Four Direction Radiography for the U Region
    Shuichi Henmi
    2013 Volume 69 Issue 1 Pages 58-70
    Published: January 20, 2013
    Released on J-STAGE: January 25, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.1.58
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    The author considered algorithms to presume the lesion location from a series of X-ray images obtained by four direction radiography without blind area for the U region of the stomach. The objects of analysis were six cases that protruding lesions were noticed in the U region. Firstly, from the length of short axis and measure of the lateral width of U region projected on the film, we presumed the length of longitudinal axis and angle between short axis and the film. Secondly, we calculated the rate of length to stomach walls from right side and left side of every image to the lateral width at the height passing through the center of the lesion. Using the lesion location calculated from these values, we presumed that the values that almost agreed between two images to be the lesion location. As the result of analysis, there were some cases that the lesion location could be presumed certainly or un-certainly, on the other hand, there were some cases that the lesion location could not be presumed. Since the form of the U region can be distorted by a change of position, or the angle between longitudinal axis and sagittal plane was changed, the error might have been made in calculation, and so it was considered that the lesion location could not be presumed.
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Clinical Technologies
  • Evaluation of Prototype for Additional Pad Packing (Polystyrene Ball Bullet) for Homogenously Fat Suppressed Magnetic Resonance Imaging
    Hiroaki Ikeguchi, Takaharu Shonai, Aya Mikami, Natsuka Yazawa, Tadashi ...
    2013 Volume 69 Issue 1 Pages 71-79
    Published: January 20, 2013
    Released on J-STAGE: January 25, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.1.71
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    Purpose: Homogeneity of static magnetic field (B0) is unstable for head and neck magnetic resonance (MR) examination; consequently, chemical shift selective fat suppression becomes inhomogeneous. There is a commercially available additional pad to attenuate the B0 inhomogeneity, but it is expensive. It has been reported that uncooked rice can be used as a material in the pad, but it has hygienic and weight problems. We searched for a material which can replace the uncooked rice, and evaluated its performance. Method: After filling various materials into the cylindrical phantom, each material was evaluated by image distortion of gradient filed echo and spin echo single-shot echo planar images. A prototype additional pad was made with a material which showed less image distortion in the phantom experiment and is easily available in clinical examination. For comparison, an uncooked rice pad with the same volume was also prepared. Fat suppressed head and neck magnetic resonance imaging (MRI) of normal volunteers were visually compared when the three additional pads, including the commercial product, were used or not. Result: The polystyrene ball bullet (BB bullet) was adopted as a material for the additional pad. The improvement of the fat suppression in the head and neck MRI was almost the same between the three additional pads. BB bullet pad was the lightest. Conclusion: BB bullet can be used as a material of additional pad attenuating the B0 inhomogeneity instead of uncooked rice.
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  • Initial Experience of Magnetic Resonance Imaging-guided Vacuum-assisted Breast Biopsy
    Hironori Tajiri, Shirou Obata, Shigetoshi Matsuo, Ichirou Isomoto, Tom ...
    2013 Volume 69 Issue 1 Pages 80-84
    Published: January 20, 2013
    Released on J-STAGE: January 25, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.1.80
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    Almost all mammary lesions are detected by a mammography and an ultrasound. However, a small part of lesions cannot be shown by only a magnetic resonance imaging (MRI). MRI-guided vacuum-assisted breast biopsy is a very useful means for the pathological diagnosis of these lesions. We performed MRI-guided vacuum-assisted breast biopsy to 4 patients with the lesions seen only by MRI. Biopsies were safely and easily performed using biopsy software (syngo BreVis). These biopsied specimens resulted cancer in 1, adenoma in 1 and benign lesions in 2. With an increase of the opportunity of MRI for the mammary lesions, we expect these lesions become increasingly large. We believe that MRI-guided vacuum-assisted breast biopsy will be an important diagnostic modality.
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  • Usefulness of Low Kilovoltage Settings in Computed Tomography Venography of Lower Limbs
    Kenji Kuramochi, Yasuyoshi Ogawa, Kousuke Chikaraishi, Kiyoko Tateishi ...
    2013 Volume 69 Issue 1 Pages 85-91
    Published: January 20, 2013
    Released on J-STAGE: January 25, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.1.85
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    It has been reported that a reduction in tube kilovoltage during computed tomography (CT) angiography results in an average reduction of the effective radiation dose. Furthermore, a lower kilovoltage has been shown as a technique dose. However, there is no fundamental data in a low-kilovoltage protocol for CT venography. Thus, the purpose of this study was to investigate contrast enhancement, image noise, and radiation exposure with lower kilovoltage on CT images scanned using phantom of lower limbs and clinical CT images. In order to grasp the effective energy in each tube voltage of the equipment used, we determined the half-value layer using aluminum attenuation coefficient. The phantom of the lower was sealed with contrast agent that was adjusted in various CT values. We scanned this phantom at 80 kVp, 100 kVp, and 120 kVp settings, and evaluated the changes in CT value. We also compared CT values, CTDIvol, contrast enhancement, and radiation exposure with 100 kVp and 120 kVp in patients with suspected pulmonary embolism or deep venous thrombosis. We found the CT value increased 30 HU with 100 kVp settings, and contrast was also improved. A reduction of radiation exposure without deterioration of image quality would be possible by lowering the kilovoltage setting in CT venography.
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  • Problem of Spectral Attenuated with Inversion Recovery Fat Suppression Method with Respiratory-gated
    Susumu Takano, Tomohiko Horie, Kazuyuki Endo, Shuhei Shibukawa, Masato ...
    2013 Volume 69 Issue 1 Pages 92-98
    Published: January 20, 2013
    Released on J-STAGE: January 25, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.1.92
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    The purpose of this study was to investigate the effect of fat suppression when we use respiratory-gated spectral attenuated with inversion recovery (SPAIR) method with respiratory-gated. We experimented on phantom and in-vivo study using simulated wave of respiratory-gated SPAIR at 1.5 tesla and 3.0 tesla. As a result, the effect of fat suppression becomes wrong with longer intervals of inspiration and expiration by wave of respiratory-gated. The signal intensity also varies with each slice. This result had the same trend on phantom and in-vivo study. The longitudinal magnetization of fat becomes a stable state when SPAIR pulse is shot more than once. However, the SPAIR method with respiratory-gated collect signal before the longitudinal magnetization of fat to be stable state, and fat suppression effect becomes bad, because the inversion time does not match the null point of the fat. Therefore, when we use SPAIR method with respiratory-gated it always causes bad fat suppression.
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Data
  • Analysis of Accidents for Magnetically Induced Displacement of the Large Ferromagnetic Material in Magnetic Resonance Systems
    Yuya Yamatani, Tsukasa Doi, Tsuyoshi Ueyama, Shigeo Nishiki, Akio Ogur ...
    2013 Volume 69 Issue 1 Pages 99-108
    Published: January 20, 2013
    Released on J-STAGE: January 25, 2013
    DOIhttps://doi.org/10.6009/jjrt.2013_JSRT_69.1.99
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    To improve magnetic resonance (MR) safety, we surveyed the accidents caused by large ferromagnetic materials brought into MR systems accidentally. We sent a questionnaire to 700 Japanese medical institutions and received 405 valid responses (58%). A total of 97 accidents in 77 institutions were observed and we analyzed them regarding incidental rate, the detail situation and environmental factors. The mean accident rate of each institute was 0.7/100,000 examinations, which was widely distributed (0–25.6/100,000) depending on the institute. In this survey, relatively small institutes with less than 500 beds tend to have these accidents more frequently (p<0.01). The institutes in which daily MR examination counts are more than 10 patients have fewer accidents than those with less than 10 daily examinations. The institutes with 6–10 MR examinations daily have significantly more accidents than that with more than 10 daily MR examinations (p<0.01). The main mental factors of the accidents were considered to be “prejudice” and “carelessness” but some advocate “ignorance.” Though we could not find significant reduction in the institutes that have lectures and training for MR safety, we should continue lectures and training for MR safety to reduce accidents due to “ignorance.”
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Special Plan—Member Interview: The People Who Contributed to the Academic Society—
Educational Lecture—Statistical Methods for Radiologic Research
Basic Lecture—From Diagnosis of the Breast to Treatment
Basic Lecture—Three-dimensional Computer Graphics
Virtual Interview for Graduate School and Laboratories
JIRA Topics
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