Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 65, Issue 9
Displaying 1-7 of 7 articles from this issue
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Opening Article
Program of the 37th Autumn Scientific Congress
Originals
  • Improvement of Determination Technique for Extracting Centerline in Coronary Artery with Calcification on CTA
    Akihiro Ikai, Yongbum Lee, Du-Yih Tsai, Isao Yamamoto, Kazunori Matsum ...
    2009 Volume 65 Issue 9 Pages 1313-1323
    Published: September 20, 2009
    Released on J-STAGE: October 14, 2009
    DOIhttps://doi.org/10.6009/jjrt.65.1313
    JOURNAL FREE ACCESS
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    The present study proposes a method for improving an existing technique used for extracting the centerlines of coronary arteries with calcifications on CTA. Through the use of the improved centerline extraction method, CPR images could be depicted accurately. In the proposed method, two dynamic range compression algorithms using two ITC for blood vessel regions and calcification regions were employed. Two dynamic range compressed CTA images obtained from the two ITC were then subtracted. After that, automatic tracing to determine the centerline for creating CPR images was performed using 3D image processing equipment. The usefulness of our proposed method was confirmed by using simulated CTA of the coronary artery with calcification. We also applied the proposed method to CTA images of 39 branches in 18 cases, and to 48 segments. Our experimental results showed that automatic tracing software pre-installed in the workstation could accurately determine the centerline of the coronary artery without being affected by the existence of calcification. Furthermore, an experienced radiological technologist evaluated the CPR images obtained by the proposed method. The results showed that most created CPR images could be used as diagnostic images after a minor revision performed manually.
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  • Evaluation of Calculation Methods of Collimator Scatter Factors in a Linear Accelerator Equipped with MLC Instead of Lower Collimators
    Tomo Kojima, Koji Sasaki
    2009 Volume 65 Issue 9 Pages 1324-1333
    Published: September 20, 2009
    Released on J-STAGE: October 14, 2009
    DOIhttps://doi.org/10.6009/jjrt.65.1324
    JOURNAL FREE ACCESS
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    In the monitor unit verification for high-energy radiation therapy, we evaluated methods of calculation of collimator scatter factors (Sc) in a linear accelerator equipped with MLC instead of lower collimators. Routinely,Sc is calculated from rectangular fields shaped by upper and lower jaws in the linear accelerator. However, this calculation method should not be used for the linear accelerator equipped with MLC instead of lower collimators. Consequently, we used a backprojected field at the flattening filter plane projected by calculation point’s eye view on each MLC. We then attempted to deviseSc by using Clarkson’s integration for these backprojected irregular fields. This method makes it possible to calculate collimator scatter factors in error of less than ±0.3% in all of sixteen measured irregular fields.
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Clinical Technology
  • Examination of Energy Spectrum Acquisition Method Using Shielded Radiopharmaceutical Syringes
    Tomoyuki Uto
    2009 Volume 65 Issue 9 Pages 1334-1342
    Published: September 20, 2009
    Released on J-STAGE: October 14, 2009
    DOIhttps://doi.org/10.6009/jjrt.65.1334
    JOURNAL FREE ACCESS
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    I previously reported on a spectrum sampling method with shielded syringes before use, although the report included only data obtained using technetium-99m. In this study, we sampled the energy spectrum in a similar manner using thallium-201, iodine-123, and gallium-67. In spectrum sampling, a radioisotopic source in a cylindrical shield is located midway between two opposed gamma-camera detectors equipped with collimators. An unshielded syringe before use emits excessive radiation and makes count rates too high to obtain accurate photopeak values. With a shielded syringe, we can sample the spectrum of radiation leaked from the needle side of the syringe and the unshielded part of its plunger side. Consequently, the detectors are exposed to lower-dose gamma rays and probably offer count rates appropriate to measure accurate photopeak values. The study results show the general validity of spectrum sampling and photopeak acquisition in our method. However, a syringe should be located accurately perpendicular to each detector; otherwise, gamma rays did not reach the detectors in some cases, resulting in measurement failures. In addition, when low-energy collimators are used for sampling from 123I sources, photopeak values depend on penetration. More accurate measurements require the use of high-energy collimators.
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