Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 63, Issue 5
Displaying 1-15 of 15 articles from this issue
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Opening Article
Educational Lecture—Interpreting Medical Images for Radiological Technologists
Basic Lectures—The Basics of Clinical Economics (2)
Clinical Technology Course
Series—Law and Medicine (2)
Report from the Scientific Research Group
  • Performance Evaluation for CT-AEC(CT Automatic Exposure Control)Systems
    Yoshihisa Muramatsu, Shu Ikeda, Kazuaki Osawa, Ryo Sekine, Nobuyuki Ni ...
    2007 Volume 63 Issue 5 Pages 534-545
    Published: May 20, 2007
    Released on J-STAGE: May 31, 2007
    DOIhttps://doi.org/10.6009/jjrt.63.534
    JOURNAL RESTRICTED ACCESS
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    Although many current CT scanners incorporate CT-AEC, performance evaluation is not standardized. This study evaluates the performance of the latest CT-AEC of each manufacturer with the aim of establishing a standard CT-AEC performance evaluation method. The design of the phantoms was based upon the operation characteristics of different CT-AECs. A cone, an ellipse, a variable-shaped ellipse, stepped phantoms, and their analysis software were devised and carried out the field test. The targets were LightSpeed VCT 64 with 2D and 3D Auto mA(GE), Aquilion 64M with Real-EC and Volume-EC(Toshiba), Sensation 64 with CARE Dose and CARE Dose 4D(Siemens), and Bulliance 16P with Dose Right(Philips). Data was acquired while varying the typical abdominal CT(with CT-AEC)scanning conditions (120 kV, 5 mm slice, standard function for abdomen, scanning range 200 mm). The acquired images were converted to the DICOM format and image noise(SD) was calculated using dedicated software. All 4 CT-AECs reduced exposure dose. For GE and Toshiba, image noise was constant and met the target. For Siemens, noise was independent of phantom shape but varied uniformly with phantom size. For Philips, noise varied with phantom size and shape, and variation degree depended on phantom thickness in scanogram direction. The results reflect the basic concept and performance characteristics of the methods. Standardization of CT-AEC performance evaluation is possible using these phantoms.
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Scientific Committee Report
Report of Research Group
JIRA Topics
Originals
  • Development and Assessment of an Automatic Quantitative Cerebral Vascular Reserve Estimation Tool for Use with Triple-injection 99mTc-ECD SPECT
    Akihiro Takaki, Katsunori Yoshioka, Satomi Teraoka, Tsutomu Souma, Kaz ...
    2007 Volume 63 Issue 5 Pages 563-569
    Published: May 20, 2007
    Released on J-STAGE: May 31, 2007
    DOIhttps://doi.org/10.6009/jjrt.63.563
    JOURNAL FREE ACCESS
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    In nuclear medicine, cerebral vascular reserve(CVR) is evaluated using technetium-99m ethyl cysteinate dimer [99mTc-ECD] and acetazolamide(ACZ). We developed a protocol involving the intravenous injection of 99mTc-ECD in three divided doses(TIE method), and have found that the cerebrovascular response to ACZ depended on time after ACZ administration. However, it was difficult to obtain high-precision quantitative SPECT images by the conventional method because of complicated image processing and image degradation accompanying image subtraction. We recently developed software known as the Automatic Quantitative CVR Estimation Tool(hereinafter referred to as Triple AQCEL), which, after the input of simple parameters, enables us to carry out automatic reconstruction of quantitative SPECT images without image degradation due to subtraction. Triple AQCEL was determined to reduce image degradation caused by subtraction and to provide valid quantitative data. Because Triple AQCEL does not require manual determination of ROI or image selection for the reconstruction of quantitative SPECT images, reproducibility of regional cerebral blood flow by 3DSRT is ensured. Since all analyses in evaluation by the TIE method are automated and the operator plays no part in them, with the resulting increase of throughput, this software will contribute to improved reproducibility of regional cerebral blood flow data, and will be useful in clinical pathophysiological assessment both preoperatively and during postoperative follow-up.
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  • Movement Analysis of Chest MR Image under Rest Breath Using Realignment of SPM
    Shigemi Kitamura, Shuji Usui, Takayoshi Horiguchi, Mitoshi Akiyama
    2007 Volume 63 Issue 5 Pages 570-576
    Published: May 20, 2007
    Released on J-STAGE: May 31, 2007
    DOIhttps://doi.org/10.6009/jjrt.63.570
    JOURNAL FREE ACCESS
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    Analyses of diaphragm and chest wall motion are good indicators to evaluate clinical status and pulmonary function before and after surgery for respiratory disease. Noninvasive MR images using fast gradient recalled echo techniques recently have received a great deal of attention for their assessment of inspiratory motion. However, it is laborious to analyze a large number of dynamic MR images. Therefore, we performed movement analyses of chest 2D MR images by using the public domain software statistical parametric mapping(SPM)Realignment sub-routine, which is commonly used for the motion correction of brain functional MRI analyses. First, dynamic 2D MR images of a glue-stick phantom were measured as a simple reciprocal movement model and were numerically analyzed by the SPM Realignment. The resulting translation to each axis coincided with the measured values. Then the dynamic images of normal volunteers under free breathing were analyzed by the same method, and we found that the inspiratory motions were quantitatively shown as the translation to each axis. These results revealed that the SPM Realignment is a useful tool for screening the magnitude and characteristics of inspiratory motion.
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  • Examination of Scan Parameters that Influence Image Quality in Three-dimensional Rotational Angiography(3D-RA)
    Naoko Naramidate, Shuichi Kodera
    2007 Volume 63 Issue 5 Pages 577-585
    Published: May 20, 2007
    Released on J-STAGE: May 31, 2007
    DOIhttps://doi.org/10.6009/jjrt.63.577
    JOURNAL FREE ACCESS
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    Because the imaging qualities of three-dimensional rotational angiography(3D-RA)are influenced by various imaging parameters, it is difficult to obtain high-quality images from 3D-RA. In this study, we compared two methods of 3D-RA, the propeller rotation technique(PRT)and the roll rotation technique(RRT)by changing image intensifier(I.I.)sizes(5, 7 and 9 inches)using a test chart and handmade phantom. The results of this study demonstrated that one of the factors determining the image quality of 3D-RA was spatial resolution. Therefore, it was important to choose an optimum I.I. size that was similar in size to collimating the region of interest(ROI)in clinical use. Another factor influencing image quality was radiographic condition, especially the setting of tube voltage. This factor was indispensable in obtaining good image contrast, but the use of high-voltage exposure was one of the reasons for lower image contrast. Therefore, if image contrast was insufficient, the image qualities of 3D-RA became worse with increasing tube voltage because the tube voltage in this study was automatically changed according to scanning method and I.I. size. In addition, because the spatial resolution of PRT was similar to that of RRT, we thought it better to use PRT because the data acquisition time(scan time)of this technique was 4 seconds shorter than that of RRT, whereas, if PRT was used, it was necessary to set a suitable rate of injection of contrast medium because the setting of the tube voltage of PRT was 10 kV higher than that of RRT. In conclusion, to improve the image qualities of 3D-RA, we considered it necessary to obtain sufficient image contrast not influenced by high tube voltage and to choose an optimum I.I. size suitable for the spatial resolution of ROI.
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  • Examination of Patient Skin Dose during Abdominal Interventional Radiology Using a GAF System
    Akitami Matsushita, Toshizo Katsuda, Taketo Kawamura, Hiroyuki Wakasa, ...
    2007 Volume 63 Issue 5 Pages 586-594
    Published: May 20, 2007
    Released on J-STAGE: May 31, 2007
    DOIhttps://doi.org/10.6009/jjrt.63.586
    JOURNAL FREE ACCESS
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    Radiation-induced skin injury caused by interventional radiology(IVR)is a deterministic effect. If exposure dose exceeds threshold dose, injuries may occur. It therefore is important to understand the maximum exposure dose in skin. The purpose of this study was to determine the maximum exposure dose and its dose distribution. Moreover, to analyze the factors from measuring the absorbed dose in the incoming radiation side, a film-type dosimeter was used. When the measured results were determined in terms of the clinical aspect, fluoroscopic time(total time)in procedure, it ranged from 3.3 to 64.0 minutes, and DSA images obtained ranged from 8 to 280 images. Absorbed dose ranged from 0.3 to 6.0 Gy, with an average dose of 3.2 Gy. It thus exceeded 2 or 3 Gy, which was the threshold dose of temporary erythematic or depilation in 10 of 14 cases. The maximum dose was 6.0 Gy for a procedure of percutaneous transhepatic obliteration. The maximum exposure dose can be determined objectively by using a film-type dosimeter. It was also possible to grasp the overall dose distribution visually
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Note
  • Technical Considerations on the Usage of a General-purpose Flatbed Image Scanner when Making a Dose-density Table
    Harumitsu Hashimoto, Masanori Nakanishi, Motoi Watanabe, Yasuhiro Tash ...
    2007 Volume 63 Issue 5 Pages 595-602
    Published: May 20, 2007
    Released on J-STAGE: May 31, 2007
    DOIhttps://doi.org/10.6009/jjrt.63.595
    JOURNAL FREE ACCESS
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    The DD-System is a dose-distribution system for analyzing the film method with a general-purpose flatbed image scanner. By analyzing the analogue digital conversion(ADC)value of each pixel acquired by the DD-system, we examined the technical problems of measurement with the scanner when making a dose-density table. When film of uniform density was measured, the ADC values distributed normally. Deviation of the values at the same pixel point on another time was about one-ten thousandth of the average. Deviation of the values from the time the scanner was turned on was in the same range. Although it may be negligible, the values measured at a peripheral area on the flatbed deviated about 2SD from the average measured at the central area. Further, deviation of the value obtained with a shade covering the outside of the irradiation field from that taken without the shade was about one thousandth. These deviations are not negligible. In the case of making a dose-density table with a DD-System and a general-purpose flatbed image scanner, the film should be set in the center of the flatbed, and the sampling area should be selected from those areas where the ADC values are distributed normally. Then proper data can be obtained and more accurate tables can be made.
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Clinical Technology
  • Accuracy of Volume Measurement of Lateral Atlanto-axial Joint by 3D-CT Facet Arthrograms
    Kyoko Saito, Mitsuhiro Satoh, Mamoru Chiba, Takeo Hikichi, Toru Tachib ...
    2007 Volume 63 Issue 5 Pages 603-608
    Published: May 20, 2007
    Released on J-STAGE: May 31, 2007
    DOIhttps://doi.org/10.6009/jjrt.63.603
    JOURNAL FREE ACCESS
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    In conventional 3D-CT image processing, the images are influenced by subjective threshold settings. The purpose of this study was to evaluate an objective threshold setting technique based on the discriminant analysis method. The concentration of contrast medium in a joint of a simulated upper cervical spine phantom was changed, and its threshold was measured from scanned data by using the discriminant analysis method, and mean CT attenuation was measured. On the other hand, an accurate image of the corresponding joint in the phantom was made, and its minimum threshold was measured. Regression analysis between the adjusted minimum threshold and mean CT attenuation of the region of contrast medium was performed. The obtained linear regression formula was applied to the threshold settings in five cases for atlanto-axial 3D-CT facet arthrogram(3D-CTF), and the accuracy of the images was examined. There was a strong correlation between the adjusted threshold and mean CT attenuation, and the obtained linear regression formula was y=0.625x-141(r2=0.991, p<0.01). This equation could be used clinically for correction of the threshold settings. We propose the following method for threshold setting of 3D-CTF: the threshold of the region of contrast medium is measured using the discriminant analysis method, then the adjusted minimum threshold for the threshold settings of 3D-CTF is calculated from mean CT attenuation. The method described herein is an objective, general-purpose methodology that is applicable to various types of 3D-CT.
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