Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 62, Issue 8
Displaying 1-13 of 13 articles from this issue
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The 61st Annual Scientific Congress
The 33rd Autumn Scientific Congress
The 33rd Autumn Scientific Congress
Educational Lecture—Interpreting Medical Images for Radiological Technologists
Clinical Technology Course
JIRA Topics
Scientific Papers
Originals
  • Measurement of Radiation Exposure to a PET Institution Driver from Patients Injected with FDG
    Fumitoshi Nakamura, Toshihiko Kanno, Hiroyuki Okada, Etsuji Yoshikawa, ...
    2006 Volume 62 Issue 8 Pages 1105-1110
    Published: 2006
    Released on J-STAGE: February 23, 2007
    DOIhttps://doi.org/10.6009/jjrt.62.1105
    JOURNAL FREE ACCESS
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    With the recent increase in FDG-PET examinations, concern has mounted regarding radiation exposure to hospital staff and the general public from patients injected with FDG. Because our PET institution is located 15 km from the hospital that provides these examinations, a driver has been designated to transport patients injected with FDG. This study was designed to measure the radiation dose to the driver from these patients (n=28) and to compare it with the estimated dose. A pocket dosimeter was used to measure radiation exposure to the driver. When the distances between the driver and patient were 1.1 m and 1.9 m, mean measured doses were 7.31 μSv and 2.26 μSv, respectively, while mean estimated doses were 8.61 μSv and 2.82 μSv, respectively, per trip. It was presumed that maximum radiation exposure per year was between 3.02 mSv (1.1 m) and 0.92 mSv (1.9 m). According to our data, the measured dose was 20% lower than the estimated dose. This discrepancy may be due to the difference between the volume source (measured dose) and point source (estimated dose).
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  • Comparison of Noise Equivalent Count Rate and Image Quality for Two-dimensional and Three-dimensional PET Scans
    Keiichi Matsumoto, Keiji Shimizu, Keishi Kitamura, Eiji Watanabe, Keny ...
    2006 Volume 62 Issue 8 Pages 1111-1118
    Published: 2006
    Released on J-STAGE: February 23, 2007
    DOIhttps://doi.org/10.6009/jjrt.62.1111
    JOURNAL FREE ACCESS
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    The aim of this study was to investigate the correlation between noise equivalent count (NEC) rates and the signal-to-noise ratio (S/N) in reconstructed images. The NEC rates were determined using uniform 20 cm and 70 cm tall, 20 cm diameter cylinders filled with 11C. The phantoms were scanned in both two-dimensional and three-dimensional modes. The reconstructed image noise was evaluated using FBP and OSEM algorithms (4 iterations and 8 subsets). The images were filtered to a final image resolution of 6.5 mm. From the reconstructed image sets, averages and standard deviations of images were generated, from which the average image S/N (=average/standard deviation) was calculated within an 18 cm central ROI. The S/N of a central slice and an end slice was compared with the NEC. The NEC was found to have a linear relationship to the image S/N of all slices, depending on differences in noise properties specific to the reconstruction algorithm. In two-dimensional mode, although the image S/N of the central slice and the edge slice showed a linear relationship with the NEC, in three-dimensional mode, the S/N of the central slice did not show a relationship with the NEC. The linear relationship was also found in both two- and three-dimensional acquisition modes, as well as for the different activity distributions. These results indicate that the NEC is not only a measure for comparing the count rate performance of imaging systems. However, an absolute evaluation is impossible to depend on reconstruction algorithm, slice number, and phantom type.
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Note
  • Estimation of the Effective Dose of Patient in Interventional Radiology: Study of Coronary Angiography
    Chikako Kawabata, Kichirou Koshida, Mayumi Hayakawa, Akira Chadani, Hi ...
    2006 Volume 62 Issue 8 Pages 1119-1126
    Published: 2006
    Released on J-STAGE: February 23, 2007
    DOIhttps://doi.org/10.6009/jjrt.62.1119
    JOURNAL FREE ACCESS
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    The applications of interventional radiology (IVR) increasingly are being used in clinical examinations, where they tend to extend examination time. In addition, the risk of occupational exposure necessarily is increasing with this technology. In this study, the dose distributions in a sliced acrylic-acid phantom involving the bore for each irradiation condition were measured using a thermoluminescence dosimeter (TLD). Four patterns of set-up for the fluoroscopy unit were chosen as references for the conditions generally used clinically. Exposure also was measured with dose area product (DAP), and we then calculated the entrance skin dose and effective dose for the patient. The results showed that the effective dose was 7.0 mSv to 8.0 mSv at LAO45° and RAO30°; 100 kV, 2.3 mSv to 3.3 mSv at LAO45° and RAO30°; 80 kV. The effective dose is greatly influenced by the setup of fluoroscopy in IVR. The change in DAP is especially influenced. We found that the relation between DAP and effective dose was corrected with the exponential function. The effective doses were not necessarily less than those of other radiation examinations, and increase. When PCI and TAE are repeated many times in IVR, we propose that the effective dose should be taken into consideration together with the skin dose for dose control management.
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Clinical Technology
  • Artifact of Indicators Equipped to Stereotactic Body Frame Scanned by 16-row MDCT Can Be Resolved
    Harumitsu Hashimoto, Masaki Yokokawa
    2006 Volume 62 Issue 8 Pages 1127-1134
    Published: 2006
    Released on J-STAGE: February 23, 2007
    DOIhttps://doi.org/10.6009/jjrt.62.1127
    JOURNAL FREE ACCESS
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    We found an artifact of the Stereotactic Body Frame's (SBF) indicators when we used diagnostic 16-row multi-detector computed tomography (MDCT) as a simulator. Stereotactic radiotherapy (SRT) requires the accuracy of each millimeter. However, a gap of 3 mm at the maximum along the Z axis was caused by this artifact. We assessed the characteristics and cause of this artifact and searched for an imaging parameter to reduce the artifact in SRT. It was considered that the artifact was formed mainly by a stair-step artifact and cone-beam artifact. We can acquired accuracy, 1 mm minimizing the beam width and pitch (10 mm/0.5625). However, exposure time was extended because minimum pitch was selected. The influence on dose calculation was negligible. We decided to use a default parameter for treatment planning, and this parameter for determining the isocenter. We found the MDCT parameters to get acceptable positional accuracy for SRT with SBF.
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Data
  • Differential Dose Albedo for High-energy X-rays on Concrete Slab
    Hideki Kato
    2006 Volume 62 Issue 8 Pages 1135-1139
    Published: 2006
    Released on J-STAGE: February 23, 2007
    DOIhttps://doi.org/10.6009/jjrt.62.1135
    JOURNAL FREE ACCESS
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    We computed the differential dose albedo (αD) for high-energy X-rays on a concrete slab when the incident angle, reflection angle, and azimuth angle were changed, by means of Monte Carlo simulation. We found that αD changed with incident, reflection, and azimuth angles to the concrete slab. On the whole, the larger the incident angle, the larger αD tended to become. If the incident angle and reflection angle were the same, the larger the azimuth angle, the smaller αD tended to become. When the incident, reflection, and azimuth angles were the same, the smaller the X-ray energy was, the larger αD became, in the order of 10 MV, 6 MV, and 4 MV X-rays.
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