Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 65, Issue 6
Displaying 1-23 of 23 articles from this issue
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Opening Article
Editorial
Originals
  • Pulmonary Functional Diagnostic Imaging Using a Dynamic Flat-panel Detector: Comparison with Findings in Pulmonary Scintigraphy
    Rie Tanaka, Shigeru Sanada, Masaki Fujimura, Masahide Yasui, Shiro Tsu ...
    2009 Volume 65 Issue 6 Pages 728-737
    Published: June 20, 2009
    Released on J-STAGE: July 14, 2009
    DOIhttps://doi.org/10.6009/jjrt.65.728
    JOURNAL FREE ACCESS
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    Pulmonary ventilation and circulation dynamics are reflected on dynamic chest radiographs as changes in X-ray translucency,i.e., pixel values. The present study was performed to develop a pulmonary functional evaluation method based on the changes in pixel value, and to investigate the clinical usefulness of our method. Sequential chest radiographs of 20 subjects (abnormal,n=12; normal,n=8) during respiration were obtained with a dynamic flat-panel detector (FPD) system. The average pixel value in each local area was measured tracking the same area. To facilitate visual evaluation, the results were mapped on the original image using a grayscale in which small changes were shown in black and large changes were shown in white. In our clinical evaluation in comparison with a pulmonary scintigraphy, pulmonary ventilation disorder was indicated as a reduction of changes in pixel values. In many patients, there was a correlation between our result and a pulmonary scintigraphy (0.7<r, 4 cases; 0.4<r≤0.7, 6 cases; 0.2<r≤0.4, 1 case; 0<r≤0.2, 1 case). The present method with real-time computer analysis is expected to be a rapid and simple method for evaluating pulmonary function and as an additional examination in conventional chest radiography.
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  • Reproducibility of Dynamic Chest Radiography with a Flat-panel Detector –Respiratory Changes in Pixel Value–
    Hiroki Kawashima, Rie Tanaka, Shigeru Sanada
    2009 Volume 65 Issue 6 Pages 738-744
    Published: June 20, 2009
    Released on J-STAGE: July 14, 2009
    DOIhttps://doi.org/10.6009/jjrt.65.738
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    Dynamic chest radiography using a flat panel detector (FPD) with a large field of view is expected to be a useful pulmonary functional evaluation method based on the respiratory changes in pixel value. For clinical use as a follow-up and therapeutic evaluation tool, the system must have a high degree of reproducibility in measurements of pixel values. The present study was performed to investigate the reproducibility of respiratory changes in pixel values. Dynamic chest radiographs of five normal subjects and one patient were obtained. Imaging was performed twice in each subject. The slope (X-ray translucency variation) was then calculated from the changes in pixel value from distance lung apex-diaphragm, and the slopes of two sequences were compared. The results showed there were no significant differences in changes in pixel value between the two sequences in all normal subject (5 males, p>0.05). The results indicated that the present method has reproducibility for measuring pulmonary function and also has potential as a tool for follow-up and therapeutic evaluation.
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Notes
  • Comparative Evaluation of 3D Images Reconstructed of MDCT or Cone-Beam CT:With Special Attentionto Depiction with Abdominal IVR
    Katsuhiko Hirota, Naoki Iwata, Yoshiharu Hirata, Toshihiro Matsuda, To ...
    2009 Volume 65 Issue 6 Pages 745-754
    Published: June 20, 2009
    Released on J-STAGE: July 14, 2009
    DOIhttps://doi.org/10.6009/jjrt.65.745
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    Diagnosis by CTHA (CT during hepatic arteriography) and CTAP (CT during arterio-portography) is indispensable in the treatment of hepatocellular carcinoma (HCC). An IVR-CT system makes it possible to perform accurate diagnosis and treatment of HCC in a short period of time. In recent years, attention has been drawn to cone-beam CT (CBCT) using a flat panel detector (FPD) angio-system, and the application of CBCT for CTAP and CTHA has been reported. However, it is well known that CBCT easily generates artifacts on the images, so it is necessary to use CBCT according to the intended purpose. The purpose of this study was to evaluate 3-D images reconstructed by MDCT or CBCT, image noise, and low-contrast resolution in a phantom with a tumor mimic model. From our results, CBCT images showed distortion and blurring, and it was difficult to visualize a tumor model of 7 mm or less. In addition CBCT can create only a small area of 3-D vascular mapping. In conclusion, it is considered that CBCT cannot be used in place of conventional CTHA or CTA for the treatment of HCC.
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  • A Characteristic of Angiographic Cone-beam CT
    Tadashi Takase, Katsunori Kinouchi, Toshio Take, Yasuo Nakazawa
    2009 Volume 65 Issue 6 Pages 755-764
    Published: June 20, 2009
    Released on J-STAGE: July 14, 2009
    DOIhttps://doi.org/10.6009/jjrt.65.755
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    Angiographic cone-beam CT, called DynaCT by SIEMENS, is a 3D imaging tool reconstructed from projection data by a rotational C-arm with a flat panel detector. It can visualize low-contrast objects such as soft tissue or small vessels as well as high-contrast structures such as enhanced vessels or bone. We need to understand its image characteristics and dose distribution during 200 degree rotation around a patient. In this research, we evaluated fundamental characteristics and dose effectiveness for optimized clinical images. DynaCT, including soft tissue information and isochronal voxel data along the z-axis, could provide enough CT-like image quality for IVR use. In addition, evaluation of accumulated dose distribution helped us to predict and avoid the occurrence of radiodermatitis. Thus, DynaCT is useful as a support and navigation tool for IVR.
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  • Combinations of Scan Parameters and Image Quality at C-arm CT for Abdominal Imaging
    Nozomu Nagasue, Yoshinori Funama, Rika Oniki, Atsushi Segawa, Satoshi ...
    2009 Volume 65 Issue 6 Pages 765-772
    Published: June 20, 2009
    Released on J-STAGE: July 14, 2009
    DOIhttps://doi.org/10.6009/jjrt.65.765
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    We measured the contrast-to-noise ratio (CNR) and evaluated low-contrast images and streak artifacts to optimize abdominal C-arm CT imaging, and we investigated the view number, acquisition matrix, and pixel depth. To measure CNR, we filled 0.125–1.0-inch cavities in an American Association of Physicists in Medicine (AAPM) CT performance phantom with a sodium chloride solution. Five radiological technologists visually evaluated the noise, signal conspicuity at low-and high-signal density, and the overall image quality using paired comparisons based on Thurstone’s law. In a given acquisition matrix, the total view number had the greatest effect on the image noise, artifacts, and signal detectability on C-arm CT images. For a given incident dose per view on the flat-panel detector (FPD), fewer images with noise and streak artifacts resulted when a larger view number was selected.
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  • Optimization of Histogram Analysis for Pediatric Digital Chest Radiography Using Flat Panel Detector System
    Tokitaka Ueno, Ryuji Nakamuta, Tadahisa Uemura, Kunihiro Matsumoto, To ...
    2009 Volume 65 Issue 6 Pages 773-781
    Published: June 20, 2009
    Released on J-STAGE: July 14, 2009
    DOIhttps://doi.org/10.6009/jjrt.65.773
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    Optical density of the lung area in pediatric digital chest radiography using an indirect flat panel detector (FPD) system were changed enormously by the influence of such factors as the size of lung area, gas of retroperitoneum, and so on. Our purpose in this study was to improve the stability of lung density on output images by means of optimizing histogram analysis. Chest images of a lung phantom were taken at various X-ray tube voltages and processed using a half-type region of interest (ROI) for the lung area. The shape of the histogram obtained by two different calculation methods including frequency distribution and cumulative relative frequency were compared, and digital chest images of 110 clinical cases in our hospital were classified into three age-groups (under 6 years old, over 6 years old and under 13 years old, and over 13 years old) and their histograms were analyzed. In conclusion, it was important that to analyze the histograms of age-groups, a cumulative relative frequency histogram should be used because the influence of X-ray tube voltage was lower than the frequency distribution histogram, and stabilized lung density under 6 years old could be obtained if the value of the imaging parameter for lung density from default was 90% to 85% or 80% because the distribution of lung area and its center value were significantly lower than in those over 13 years old.
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Clinical Technology
  • Measurement of Residual Effect in the Amorphous Selenium Flat Panel Detector System
    Kojiro Nishijima, Katsuhiko Ueda, Shohei Kudomi, Taizo Sanada
    2009 Volume 65 Issue 6 Pages 782-787
    Published: June 20, 2009
    Released on J-STAGE: July 14, 2009
    DOIhttps://doi.org/10.6009/jjrt.65.782
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    The purpose of this study was to evaluate the residual effect generated by the amorphous selenium flat panel detector system (a-Se FPD). A residual effect occurs as a result of the addition of delayed electrons by previous X-ray irradiation joining the signal and change in detector sensitivity caused by hole-electron recombination or trapped electrons in a-Se. To evaluate the effect of previous radiation exposure, we irradiated a-Se FPD that were half-shielded by a 3 mm thick lead plate. A residual effect was generated in irradiated areas, with the unirradiated areas serving as reference points. Next, we removed the lead plate and took a new image using uniform irradiation. The difference in pixel value between irradiated and nonirradiated areas was measured using a variety of time intervals between each exposure. Through a comparison of pixel values from images taken over various time intervals, we discovered our system needs 20 hours to return to a normal state and become capable of producing a residual-free image.
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  • Evaluation of FOV Size on Cerebral Three-dimensional Rotational Digital Subtraction Angiography with Flat Panel Detector System
    Tomohiro Kaneko, Hideki Kato, Takanori Hara
    2009 Volume 65 Issue 6 Pages 788-794
    Published: June 20, 2009
    Released on J-STAGE: July 14, 2009
    DOIhttps://doi.org/10.6009/jjrt.65.788
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    In interventional neuroradiology, three-dimensional rotational digital subtraction angiography (3D-DSA) is very useful for the spatial grasp of the location and size of an intracranial cerebral aneurysm. The purposes of this study were to evaluate the property of three-dimensional image dependence on the respective field of view (FOV) size in a flat-panel detector (FPD) using vessel phantoms, and to optimize clinically. The indices of three-dimensional image properties such as profile curve (FWHM, FWTM), digital value, and image noise were evaluated using a vessel phantom with a different diameter. As a result, in the case of a 6-inch FOV size of the FPD, the relative diametral rate of change from the actual value of the vessel phantom was least for all FOV sizes. This study demonstrated that the difference in FOV size in 3D-DSA affects the three-dimensional object’s reproducibility. Furthermore, as for this 3D-DAS system, three-dimension images such as a VR image might be processed more faithfully, since an FOV size of 6 inches has the highest reproducibility of objects.
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  • Angiography: Clinical Evaluation and Physical Characteristics of FPD
    – The Clinical Impact Caused by Detector Characteristics –
    Takao Ichida, Shohei Sasaki, Masachika Shougaki, Kenji Okusako, Takayo ...
    2009 Volume 65 Issue 6 Pages 795-804
    Published: June 20, 2009
    Released on J-STAGE: July 14, 2009
    DOIhttps://doi.org/10.6009/jjrt.65.795
    JOURNAL FREE ACCESS
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    We have been engaged in clinical work using DSA, the first in the world, under a joint study agreement with Hitachi Medical Corporation on the use of the Flat Panel Detector (FPD) since 2001. We are now in the stage where a certain evaluation process has been finished, but the FPD performance study in angiography has just begun, and, therefore, its clinical evaluation results are very few. Therefore, we studied the relativity between clinical images and physical characteristics in order to examine the characteristics of FPD by referencing them to clinical images. We did an evaluation of the clinical images to which their physical characteristics such as granularity, resolution, contrast, etc., are reflected by comparing FPD and I.I. images.
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Technological Commentary
Special Contribution
Basic Lecture—Physical Image Quality Assessment in Digital Radiography
JIRA Topics
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