Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 71, Issue 2
Displaying 1-10 of 10 articles from this issue
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Opening Article
Original
  • Kernel Eigenspace Template Matching for Detection of Lacunar Infarcts on MR Images
    Saki Murakawa, Ayaka Tanigawa, Yoshikazu Uchiyama, Chisako Muramatsu, ...
    2015 Volume 71 Issue 2 Pages 85-91
    Published: 2015
    Released on J-STAGE: February 27, 2015
    DOIhttps://doi.org/10.6009/jjrt.2015_JSRT_71.2.85
    JOURNAL FREE ACCESS
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    Detection of lacunar infarcts is important because their presence indicates an increased risk of severe cerebral infarction and dementia. However, accurate identification of lacunar infarcts is often difficult for radiologists. Our previous computer-aided detection (CAD) scheme achieved a sensitivity of 96.8% with 0.76 false positives (FPs) per slice. However, further reduction of FPs remained an issue for the clinical application. The purpose of this study is to improve our CAD scheme by using kernel eigenspace template matching. First, we selected the regions of interest (ROIs) around the candidate regions detected in our previous method. A kernel eigenspace was then made by using kernel principal component analysis of the training data set. A test ROI was projected onto the same kernel eigenspace as the training data set. The cross-correlation coefficients between the test ROI and all the training ROIs were calculated on the kernel eigenspace. By comparing the two maxima of coefficients with a lacunar ROI and an FP ROI, the test ROI was classified. By using the proposed method, the quantity of the templates became 1.9% of that in template matching on the real space and 31. 9% of FPs could be eliminated while keeping the same sensitivity; nevertheless 30.3% of FPs were eliminated when we employed the eigenspace template matching under the same condition. Therefore, kernel eigenspace template matching could improve FP rate without a significant reduction in the true positive rate.
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Note
  • Validation and Analysis of Dose Distributions in a New and Entirely Redesigned Cobalt-60 Stereotactic Radiosurgery Units
    Hisato Nakazawa, Yukio Uchiyama, Masataka Komori
    2015 Volume 71 Issue 2 Pages 92-98
    Published: 2015
    Released on J-STAGE: February 27, 2015
    DOIhttps://doi.org/10.6009/jjrt.2015_JSRT_71.2.92
    JOURNAL FREE ACCESS
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    The objective of this study was to evaluate the reproducibility of dose distributions in stereotactic treatment planning throughout Gamma Knife (GK) stereotactic radiosurgery (SRS) procedures in both GK model C and Perfexion (PFX). An originally-developed phantom and a radiochromic film were used for obtaining actual dose distributions. The phantom, with inserted films, was placed on a Leksell skull frame. Computed tomography (CT) was then acquired with a stereotactic localizer box attached to the frame, dose planning was made using the Leksell GammaPlan treatment planning system, and the phantom was ended up as beam delivery on an equal with clinical radiosurgery process. The reproducibility of the dose plan was provided by distance to agreement (DTA) values between planned and irradiated dose distributions calculated by dedicated film analysis software. The DTA values were determined for the isodose lines at 30%, 50%, 70%, and 90% of the maximum dose. In our study, the reproducibility of dose distributions in GK PFX was lower than in GK model C. As the results common to both units, the mean values of middle dose area (50% isodose) were about half the values of high (90% isodose) and low (30% isodose) dose area. Therefore validation of dose distributions is absolutely essential in commissioning of GK PFX. In addition, when risk organs are close to the target, dose prescription should be normalized for middle isodose line.
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Data
  • Incident Reports Related to Tasks Performed by Radiological Technologists: An Analysis of Ten Years of Incident Reports
    Masahiro Hashida, Junji Shiraishi
    2015 Volume 71 Issue 2 Pages 99-107
    Published: 2015
    Released on J-STAGE: February 27, 2015
    DOIhttps://doi.org/10.6009/jjrt.2015_JSRT_71.2.99
    JOURNAL FREE ACCESS
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    In the past 10 years at our university hospital, 202 incident reports related to tasks performed by radiological technologists were posted. In order to investigate the causes and trends of these incidents, we classified the incident reports into four groups based on the event content, level of harm caused to the patient, years of experience of the concerned radiological technologist, and relevant departmental section. In the event content group, ‘a malfunctioning device’ was the most common event (26.2%), whereas the other events were ‘wrong examination procedure or therapy’ (15.3%), ‘patient fall’ (10.9%), ‘procedure-patient mismatch’ (8.4%), ‘accidental removal of patients’ tubes or other intravenous devices’ (7.9%), and ‘bringing metallic material into the magnetic resonance imaging (MRI) room’ (7.4%). In the level of harm caused to the patient group, level one events occurred frequently. Radiological technologists with 6–16 years of experience reported incidents most frequently. With regard to the relevant departmental section where the incidents occurred, departments with the highest number of reports were ranked as follows in descending order: general X-ray examination section, MRI section, radiation therapy section, nuclear medicine (NM) section, computed tomography (CT) section, angiography section, and fluoroscopy section. The following events in each corresponding section require careful monitoring: patient fall in the general X-ray examination section and NM section, bringing metallic material into the MRI room, malfunctioning devices in the radiation therapy section, accidental removal of the patient's tubes in the CT section, incorrect handling of the automatic contrast medium injector in the angiography section, and damage of device or article in the fluoroscopy section.
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Educational Lecture—Monte Carlo Simulation for Radiological Technology
Basic Lecture—Disease of the Brain: From Diagnosis to Treatment
Students′ Pages
Dispatch Reports to International Conferences
Scientific Exchanges Committee Report
JIRA Topics
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