Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 70, Issue 1
Displaying 1-17 of 17 articles from this issue
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Opening Article
New Year Round Table Discussion
Originals
  • The Decision Process of Notification Value by the Dose Index Registry System in X-ray Computed Tomography
    Masafumi Shinozaki, Yoshihisa Muramatsu, Toru Sasaki
    2014 Volume 70 Issue 1 Pages 11-18
    Published: January 20, 2014
    Released on J-STAGE: January 27, 2014
    DOIhttps://doi.org/10.6009/jjrt.2014_JSRT_70.1.11
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    A new technical standard for X-ray computed tomography (CT) has been published by the National Electrical Manufacturers Association (NEMA) that allows the Alert Value and Notification Value for cumulative dose to be configurable by CT systems operators in conjunction with the XR-25 (Dose check) standard. In this study, a decision method of the Notification Values for reducing the radiation dose was examined using the dose index registry (DIR) system, during 122 continuous days from August 1, 2012 to November 30, 2012. CT images were obtained using the Discovery CT 750HD (GE Healthcare) and the dose index was calculated using the DoseWatch DIR system. The CT dose index-volume (CTDIvol) and dose-length product (DLP) were output from the DIR system in comma-separated value (CSV) file format for each examination protocol. All data were shown as a schematic boxplot using statistical processing software. The CTDIvol of a routine chest examination showed the following values (maximum: 23.84 mGy; minimum: 2.55 mGy; median: 7.60 mGy; 75% tile: 10.01 mGy; 25% tile: 6.54 mGy). DLP showed the following values (maximum: 944.56 mGy·cm; minimum: 97.25 mGy·cm; median: 307.35 mGy·cm; 75% tile: 406.87 mGy·cm; 25% tile: 255.75 mGy·cm). These results indicate that the 75% tile of CTDIvol and DLP as an initial value proved to be safe and efficient for CT examination and operation. We have thus established one way of determining the Notification Value from the output of the DIR system. Transfer back to the protocol of the CT and automated processing each numeric value in the DIR system is desired.
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  • Development of a Batched Image Delete System for Multi-vender Picture Archiving and Communication System Environment
    Kenji Yamada, Masafumi Amano, Masao Yuasa, Yuichiro Yamamoto, Akihisa ...
    2014 Volume 70 Issue 1 Pages 19-25
    Published: January 20, 2014
    Released on J-STAGE: January 27, 2014
    DOIhttps://doi.org/10.6009/jjrt.2014_JSRT_70.1.19
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    A picture archiving and communication system (PACS) for multi-vendor imaging servers is useful, since it can provide a variety of image-processing services. However, to delete an image file in the PACS, it is necessary to delete not only the image but all its associated images that are stored in multiple servers: this is a lengthy and painstaking process. To reduce this workload, we have developed a system consisting of a computer program with a graphical user interface that can delete the target image and all related images by means of batch processing. The developed system creates an extensible markup language (XML)-format file that describes the operation for deleting an image and forwards the XML file to the main server. Using a Windows file-sharing system (SMB/CIFS), each server shares the XML file and deletes the images in its own database in response to the instructions described in the XML file. We can also rigorously manage information concerning the deleted images using the information that is output from the main server to external storage. We also discuss the degree of load reduction in our system compared with that of ordinary systems.
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  • Development of Cloud Chamber Having Thin-film Entrance Windows and Proposal of Practical Training for Beginners Using X-ray Equipment and Unsealed Radioactive Material
    Yuki Konishi, Hiroaki Hayashi, Kazuki Takegami, Ikuma Fukuda, Junji Ue ...
    2014 Volume 70 Issue 1 Pages 26-33
    Published: January 20, 2014
    Released on J-STAGE: January 27, 2014
    DOIhttps://doi.org/10.6009/jjrt.2014_JSRT_70.1.26
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    A cloud chamber is a detector that can visualize the tracks of charged particles. Hayashi, et al. suggested a visualization experiment in which X-rays generated by diagnostic X-ray equipment were directed into a cloud chamber; however, there was a problem in that the wall of the cloud chamber scattered the incoming X-rays. In this study, we developed a new cloud chamber with entrance windows. Because these windows are made of thin film, we were able to direct the X-rays through them without contamination by scattered X-rays from the cloud chamber wall. We have newly proposed an experiment in which beta-particles emitted from radioisotopes are directed into a cloud chamber. We place shielding material in the cloud chamber and visualize the various shielding effects seen with the material positioned in different ways. During the experiment, electrons scattered in the air were measured quantitatively using GM counters. We explained the physical phenomena in the cloud chamber using Monte Carlo simulation code EGS5. Because electrons follow a tortuous path in air, the shielding material must be placed appropriately to be able to effectively block their emissions. Visualization of the tracks of charged particles in this experiment proved effective for instructing not only trainee radiological technologists but also different types of healthcare professionals.
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Note
  • Development of a Quality Assurance Phantom for Brachytherapy: The Feasibility of Daily Check with the Phantom
    Yudai Kai, Ryuji Murakami, Masato Maruyama, Yuji Nakaguchi, Nozomu Nag ...
    2014 Volume 70 Issue 1 Pages 34-40
    Published: January 20, 2014
    Released on J-STAGE: January 27, 2014
    DOIhttps://doi.org/10.6009/jjrt.2014_JSRT_70.1.34
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    Purpose: We developed a quality assurance (QA) phantom to enable easy confirmation of radiation source output measurements of a high dose rate 192Ir intracavitary brachytherapy unit in gynecology. The purpose of this study was to evaluate the feasibility of daily checks using the QA phantom. Methods and materials: The QA phantom was designed with tough water phantoms to hold a Farmer-type ionization chamber, with semiconductor detectors used as in vivo dosimeters to measure rectal dose, and three transfer tubes for gynecology. To test the reliability of our QA phantom for the detection of abnormalities in source output or semiconductor detectors, we applied different doses. Results: Variations due to different settings of the QA phantom were within 2%. The temporal variations were less than 2% and 5% in the Farmer-type ionization chamber and semiconductor detectors, respectively. Interobserver variations were below 3%. Conclusions: With tolerance levels of 2% and 5% for a Farmer-type ionization chamber and semiconductor detectors, respectively, a QA phantom is potentially useful for easily detecting abnormalities by applying daily checks of the brachytherapy unit.
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Clinical Technologies
  • Computed Tomography Colonography Image Assessment Using Colon Phantom-effects of Reconstructed Slice Thickness
    Yoshihiro Futamata, Naoyuki Akagi, Tsukasa Sugawara, Shunichi Nakamura
    2014 Volume 70 Issue 1 Pages 41-50
    Published: January 20, 2014
    Released on J-STAGE: January 27, 2014
    DOIhttps://doi.org/10.6009/jjrt.2014_JSRT_70.1.41
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    Computed tomography colonography (CTC) is a robust and reliable imaging test of the colon. Recent studies show good sensitivity for the identification of nonpolypoid (flat) lesions as well. The purpose of this study was to determine the accuracy and reproducibility of a volume-rendering (VR) and virtual gross pathology (VGP) technique for detecting a polypoid lesion phantom by varying slice thickness. The scan of a simulated house-made phantom was performed using a 16-slice CT scanner with varying combinations of tube voltage (120 kVp), effective exposure (100 mAs), detector configuration (16×0.75 mm), rotation time (0.75 s), helical pitch (0.688, 0.938, 1.066 and 1.188), reconstruction kernel (A, B and C), and section thickness/reconstruction interval (0.8/0.4, 1.0/0.5 and 1.5/0.75 mm). All image data were transferred to a three-dimensional workstation to assess multi-planar reformation (MPR), VR and VGP. Accuracy of volume measurement using the VR technique for quantitative analysis was compared using a paired t-test. Four radiological technologists also independently evaluated the visual score using the VGP technique for qualitative analysis, and their evaluations were compared using one-way analysis of variance with Fisher’s protected least significant difference post-hoc test. There was a statistically significant difference in reproducibility between the three different slice thicknesses as to volume measurement and observer performance test (p<0.01 and p<0.05, respectively). Furthermore, the reproducibility improved when using thinner slices. In conclusion, VR and VGP techniques using a slice thickness of 0.8 mm made it possible to maintain accuracy and reproducibility when using CTC to detect polypoid lesions.
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  • Availability of Using Diaphragm Matching in Stereotactic Body Radiotherapy (SBRT) at the Time in Breath-holding SBRT for Liver Cancer
    Daisuke Kawahara, Syuichi Ozawa, Takeo Nakashima, Masamichi Aita, Shin ...
    2014 Volume 70 Issue 1 Pages 51-56
    Published: January 20, 2014
    Released on J-STAGE: January 27, 2014
    DOIhttps://doi.org/10.6009/jjrt.2014_JSRT_70.1.51
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    Purpose: Liver image guided radiation therapy (IGRT) based on bone matching risks generating serious target positioning errors for reasons of lack of reproducibility of expiration breath hold. We therefore investigated the feasibility of 3D image matching between planning CT images and pretreatment cone-beam computed tomography (CBCT) images based on diaphragm surface matching. Method: 27 liver stereotactic body radiotherapy (SBRT) cases in whom trancecatheter arterial chemoembolization (TACE) had been performed in advance of radiotherapy were manually image-matched based on contrast, Lipiodol used in the TACE as the marker of the tumor, and the relative coordinates of the isocenter obtained by contrast matching, defined as the reference coordinate. The target positioning difference between diaphragm matching and bone matching were evaluated by using relative coordinates of the isocenter from the reference obtained for each matching technique. Results: The target positioning error using diaphragm matching and bone matching was 1.31±0.83 and 3.10±2.80 mm in the cranial-caudal (C-C) direction, 1.04±0.95 and 1.62±1.02 mm in the anterior-posterior (A-P) direction, and 0.93±1.19 and 1.12±0.94 mm in the left-right (L-R) direction, respectively. The positioning error due to diaphragm matching was significantly smaller than for bone matching in the C-C direction (p<0.05). Conclusion: IGRT based on diaphragm matching has potential as an alternative image matching technique for the positioning of liver patients.
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  • Preventive Measures Against Human Error Based on the Classification of the Adverse Events
    Kenji Nishimura
    2014 Volume 70 Issue 1 Pages 57-65
    Published: January 20, 2014
    Released on J-STAGE: January 27, 2014
    DOIhttps://doi.org/10.6009/jjrt.2014_JSRT_70.1.57
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    It is impossible to entirely eliminate human error; however, systematic attempts have been made to comprehensively minimize accidents originating in human error. It appears that the “work classification” we proposed previously is not able to reduce adverse events, fifty percent of which were duty confirmation failures. We have therefore reviewed and classified the causes of human error from the perspective of working conditions to create a simpler and more preventative strategy. Text-mining analysis was applied to speech part classification to reveal areas with room for improvement. In an objective approach, a conduct code was created and put into practice, based on the common features revealed from a classification of human error in the examples investigated. The average number of accidents per year was reduced from 36 to 24, and those due to human error per year were reduced from 17.6 to 11. This objective approach appears to achieve a reduction of adverse events, including those caused by human error. However, these results were obtained over only one year, in a single-center analysis, and thus, widespread and continuous enforcement would be needed to demonstrate the validity of this objective approach to the prevention of human error.
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Data
  • Evaluation Study of Abnormal Detectability with Thurstone and Scheffé (Nakaya) of Paired Comparison Method Using Chest Phantom
    Yasuo Mochizuki
    2014 Volume 70 Issue 1 Pages 66-72
    Published: January 20, 2014
    Released on J-STAGE: January 27, 2014
    DOIhttps://doi.org/10.6009/jjrt.2014_JSRT_70.1.66
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    Monitors are increasingly being used as diagnostic imaging devices. In this study, using an all-purpose liquid-crystal display (LCD), the rate of detection of abnormalities was investigated using Thurstone’s and Scheffé’s (Nakaya) paired comparison methods. A chest phantom was prepared as a test sample with acryl and aluminum plates and intensities suggesting small adenocarcinomas. For the acquisition conditions for computed radiography, after setting the baseline at a dose at which the film density of the standard screen-film system at the same as those for the lung, costal bone, and mediastinum, 5 steps of 2-fold serial doses were then set: 1/4, 1/2, 1, 2, and 4. The test sample was observed by 10 students. On the Thurstone scale, detectability decreased with a decrease in the dose in the lung, costal bone, and mediastinum. When the significance of differences between the values at adjacent doses was investigated using the yardstick method, using Scheffé’s method revealed a significant difference between the 4- and 2-fold doses and between the 1/2 and 1/4 doses in the pulmonary region. A significant difference was also noted between the baseline and 1/2 doses in the mediastinum. Changes in the order of the scale values may not occur in the intervals in which significant differences were noted using Scheffé’s methods.
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The 69th Annual Scientific Congress
Contribution
Special Article for Vol. 70
Basic Lecture—Heart Disease: From Diagnosis to Treatment
Science Exchanges Committee News
JIRA Topics
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