Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 63, Issue 8
Displaying 1-15 of 15 articles from this issue
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Opening Article
Originals
  • Development of an Algorithm for the Detection of Early Signs of Cerebral Ischemia on CT Images
    Noriyuki Takahashi, Yongbum Lee, Du-Yih Tsai, Kiyoshi Ishii
    2007 Volume 63 Issue 8 Pages 835-842
    Published: August 20, 2007
    Released on J-STAGE: October 04, 2007
    DOIhttps://doi.org/10.6009/jjrt.63.835
    JOURNAL FREE ACCESS
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    This paper describes an approach to automatically detect the parenchymal hypoattenuation of hyperacute stroke in nonenhanced computed tomography (CT) images. This technique is based on a comparison between the CT values histograms of right and left brains. A subtraction curve that was regarded as an output value was calculated by subtracting the right-hemispherical histogram from the left-hemispherical histogram obtained from one of the region-of-interest (ROI) sets on an image. The output value was used to assess whether hypoattenuation exists on CT images with a threshold value. If judged abnormal, a rectangular region including a whole or partial hypoattenuation area was detected from the ROI. Twenty-six cases with hypoattenuation and 30 cases without hypoattenuation were included in this study. As a result of our experiments, the sensitivity of this method in detecting hypoattenuation was found to be 92%, with approximately 0.16 false-positive per image. Our preliminary experimental results indicated that the proposed technique can be used for the automated detection of parenchymal hypoattenuation of hyperacute stroke on nonenhanced CT images. [Article in Japanese]
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  • Bone Fusion Algorithm: A New Tool to Support Decision Making
    Satoru Oishi, Kieran J. Murphy, Mayumi Oka, Philippe Gailloud
    2007 Volume 63 Issue 8 Pages 843-851
    Published: August 20, 2007
    Released on J-STAGE: October 04, 2007
    DOIhttps://doi.org/10.6009/jjrt.63.843
    JOURNAL FREE ACCESS
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    Three dimensional angio (3D-Angio) is indispensable in neuroradiology, especially for examinations and interventions of cerebral-aneurysms. 3D-Angio has two modes, 3D-DSA and 3D-DA. The former mode is used to determine vessel structures in detail, and the latter is good at simultaneously determining relationships between vascular and osseous structures. However, it is sometimes difficult to determine these relationships with 3D-Angio if they are close together. The relationship between the skull base and adjacent aneurysm is an essential factor in determining treatment strategy. In order to make this determination, we have developed the Bone Fusion function, which reconstructs vessel and osseous structures separately from rotational DSA data and its mask sequence data, respectively, and two independent 3D data sets are fused in one 3D representation. There are three display modes: fusion, vessel only, and bone only, and those structures are clearly identified by different colors on the fusion images. The Bone Fusion function was applied to hundreds of clinical cases in which 3D-DSA and 3D-DA were used. The Bone Fusion provided important information to determine treatment strategy, although those factors were sometimes lost with 3D-DSA and 3D-DA when the studied vasculatures were adjacent to bone. It was especially useful to apply the Bone Fusion function to aneurysms or tumors adjacent to the skull base. [Article in Japanese]
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  • Estimation of Personal Dose Based on the Dependent Calibration of Personal Dosimeters in Interventional Radiology
    Hiroshige Mori, Kichiro Koshida, Katsuhiro Ichikawa
    2007 Volume 63 Issue 8 Pages 852-861
    Published: August 20, 2007
    Released on J-STAGE: October 04, 2007
    DOIhttps://doi.org/10.6009/jjrt.63.852
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    The purpose of present study is, in interventional radiology (IVR), to elucidate the differences between each personal dosimeter, and the dependences and calibrations of area or personal dose by measurement with electronic dosimeters in particular. We compare space dose rate distributions measured by an ionization survey meter with the value measured by personal dosimeter: an optically stimulated luminescence, two fluoroglass, and two electronic dosimeters. Furthermore, with electronic dosimeters, we first measured dose rate, energy, and directional dependences. Secondly, we calibrated the dose rate measured by electronic dosimeters with the results, and estimated these methods with coefficient of determination and Akaike's Information Criterion (AIC). The results, especially in electronic dosimeters, revealed that the dose rate measured fell by energy and directional dependences. In terms of methods of calibration, the method is sufficient for energy dependence, but not for directional dependence, because of the lack of stable calibration. This improvement poses a question for the future. The study suggested that these dependences of the personal dosimeter must be considered when area or personal dose is estimated in IVR. [Article in Japanese]
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  • Method of Segmenting Inferior Horns of Lateral Ventricles Using Active Contour Models
    Masumi Hattori, Shuji Koyama, Yoshie Kodera
    2007 Volume 63 Issue 8 Pages 862-870
    Published: August 20, 2007
    Released on J-STAGE: October 04, 2007
    DOIhttps://doi.org/10.6009/jjrt.63.862
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    Recent research has suggested that the measurement of regional atrophy in the structure of the medial temporal lobe is a promising way to discriminate Alzheimer-type dementia patients from healthy control subjects. There are some reports that the inferior horns of the lateral ventricles are expanded by atrophying the structure of the medial temporal lobe. We developed a technique to automatically detect the region of the inferior horns of the lateral ventricles by gray-level thresholding and morphological processing. However, there were some incorrect regions in this method. Accordingly, we proposed a technique for which active contour models (ACM) were used. Our ACM incorporates the improved edge-based image and the external constraint to improve convergence and to reduce its dependence on initial estimation. In this study, we present the details of an algorithm that traces the contours of the inferior horns of the lateral ventricles and its performance relative to manual methods. The average degree of correspondence between the extract region and manual trace was measured in 30 inferior horns of 15 subjects. The average degree of correspondence of the proposed method was about 4% higher than that of the conventional method. These results suggest that the proposed method is more accurate than the conventional method. [Article in Japanese]
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Notes
  • Method of Calculating Patient Skin Surface Dose in Transcatheter Arterial Embolization
    Go Hitomi, Yasushi Ohata, Eiji Matsuda, Tatsushi Tomomitsu
    2007 Volume 63 Issue 8 Pages 871-876
    Published: August 20, 2007
    Released on J-STAGE: October 04, 2007
    DOIhttps://doi.org/10.6009/jjrt.63.871
    JOURNAL FREE ACCESS
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    The usefulness of interventional radiology (IVR) in clinical practice is well known. However, patient dose in IVR has recently been increased as a result of the prolongation of fluoroscopic time and the increased number of radiographies. We studied a simple method of calculating skin surface dose in patients who underwent transcatheter arterial embolization (TAE) for the treatment of hepatocellular carcinoma by obtaining the value of a dose area product meter attached to the digital subtraction angiography system. In 20 subjects (15 men and 5 women, aged an average of 68.2±7.3 years, respectively) who underwent TAE, exposure conditions (tube voltage, tube current, time, and size of image intensifier) in a time series and last value indicated on the dose area product meter were recorded. A dosimetric phantom was placed at a position the same as that of the patient for TAE, the surface dose (SD) of the phantom was measured under various exposure conditions, and SD per unit mAs (SD/mAs) was obtained. Then the skin surface dose in each subject was estimated from the values of the exposure condition and SD/mAs. A high correlation was observed between the last value (x) on the dose area product meter and the estimated skin surface dose (y) (r=0.933), and the following regression equation was derived: y=0.005x-0.589. The skin surface dose calculated using the regression equation was compared with that obtained by the method recommended by the Japan Association on Radiological Protection in Medicine (JARPM), considering the value estimated from the value of exposure conditions with SD/mAs as the gold standard. The results indicated that the error in the method using the regression equation was significantly lower than that of the JARPM method (18.3±14.0% and 75.5±66.0%, respectively, p<0.01). In conclusion, the skin surface dose in TAE could be monitored with high precision using the value of the dose area product meter by obtaining the regression formula between the value of the dose area product meter and the skin surface dose estimated with the phantom values. [Article in Japanese]
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  • Evaluation of the Accuracy of a Compensating Filter Based on Compact NC-Mill for Radiation Therapy
    Hiroshi Oguchi, Masanori Miyazawa, Masaomi Takizawa
    2007 Volume 63 Issue 8 Pages 877-887
    Published: August 20, 2007
    Released on J-STAGE: October 04, 2007
    DOIhttps://doi.org/10.6009/jjrt.63.877
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    The present report describes the fabrication technique and dosimetry aspects of a desktop numerically controlled milling machine (NC-Mill) based a compensator system that uses lead clay (Shield/Cray, Reactor Experiments, Inc., U.S.A.). Effective path lengths of patients were determined for CT image sets using the ray-tracing technique and converted to compensator thickness with the equivalent TMR method. Rigid urethane foam was processed with the NC-Mill to produce a mold for filters, and the lead clay was adopted as the compensating material. The dose distribution was measured on the compensating plane of an anthropomorphic phantom and a stair-step PMMA phantom. It was found that the radiation field with inhomogeneous dose was as high as 30%±3% with the compensating filters. In addition, when the absorbed dose at the central axis of 52 compensating filters that were used clinically was measured, 75.0% showed an error of less than ±3%, and 3.8% showed the maximum dose error: >±5%. Overall, the present system was capable of producing dose uniformity to within ±5% for a stair-step phantom, an anthropomorphic phantom, and clinical situations. [Article in Japanese]
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Data
  • Investigation of a CT Value Electron Density Conversion Method in Radiotherapy Planning CT
    Yukihiro Matsuda, Yukio Kiyomiya, Kazuhide Matsuda, Yoshihiro Enokido
    2007 Volume 63 Issue 8 Pages 888-894
    Published: August 20, 2007
    Released on J-STAGE: October 04, 2007
    DOIhttps://doi.org/10.6009/jjrt.63.888
    JOURNAL FREE ACCESS
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    To obtain heterogeneous corrections, it is necessary to convert computed tomography (CT) values into electron density. However, differences in the current conversion tables of the method of acquisition for each institution are not clear. Therefore, we sent a questionnaire survey to 200 radiotherapy institutions in the Kanto area regarding heterogeneous correction data acquisition. When these conversion tables were created, many institutions used phantoms for conversion, and 85% of institutions borrowed them from the factories. On the other hand, some institutions used the factory values as the other conversion method. In the conversion tables of the various institutions, we recognized large differences between institutions, in that relative electronic density (Rel.ED) was greater than 1.0. When we assumed the CT value of bone to be 793 HU, the mean relative electron density at 120 kV was 1.46±0.09, with a minimum of 1.36 and maximum of 1.82. We have recognized the need to create guidelines detailing these methods of evaluation. [Article in Japanese]
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The 34th Autumn Scientific Congress
Educational Lecture—Interpreting Medical Images for Radiological Technologists
Basic Lectures—The Basics of Clinical Economics (4)
Clinical Technology Course
Series—Law and Medicine (4)
Science Exchanges Committee Report
JIRA Topics
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