Japanese Journal of Medical Physics (Igakubutsuri)
Online ISSN : 2186-9634
Print ISSN : 1345-5354
ISSN-L : 1345-5354
Volume 27, Issue 2
Displaying 1-3 of 3 articles from this issue
  • Hironori KOJIMA, Takatsugu MAGARA, Yasuhiro FUKUSHIMA, Minoru ISHIGAMI ...
    2007 Volume 27 Issue 2 Pages 50-57
    Published: November 30, 2007
    Released on J-STAGE: September 24, 2012
    JOURNAL FREE ACCESS
    In radiation therapy, there is no suitable method to confirm either the three-dimensional irradiated area or the absorbed dose during irradiation. If there were such a method it would allow verification of the absorbed dose as well as help to avoid extraneous irradiation. We previously proposed a method utilizing annihilation photons generated by therapeutic photon beams to measure the irradiated area directly during irradiation. In the present study, we designed and fabricated a fast YAP: Ce scintillation counter which uses a compact photosensor to measure annihilation photons. The energy resolution and detection efficiency were obtained experimentally using a 22Na planar source. We measured count rates of background radiation by using the detector and estimated those of background radiation from an e-LINAC by correcting for detection efficiency. The obtained energy resolution of the YAP: Ce scintillation detector was 12.1±3.5% and its detection efficiency was 28.3±5.3%. The counting rates of background radiation from e-LINAC were approximately from 108 to 109 cps, and were proportional to the e-LINAC dose rate. Our developed detector had a high sensitivity, good time resolution and compact size which allows for easy radiation shielding. Therefore, we concluded that it was both practical and effective for the measurement of the position-distribution of annihilation photons.
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  • Kenya MURASE, Shohei MIYAZAKI
    2007 Volume 27 Issue 2 Pages 58-70
    Published: November 30, 2007
    Released on J-STAGE: September 24, 2012
    JOURNAL FREE ACCESS
    Using computational fluid dynamics (CFD), we demonstrated a method for numerical analysis of the transcapillary exchange of contrast agent (CA) in a tissue homogeneity (TH) model consisting of the intravascular space (IVS) and extravascular space (EVS). To validate the CFD method, we compared the time-dependent concentrations of CA in the IVS (Ci(t)) and the EVS (Ce(t)) obtained by it with analytical solutions to the TH model using the Laplace transform for a simulated arterial input function. When the diffusion of CA in the capillary was taken into account in the CFD method, there was a good agreement between its results and those of the analytical solutions. As illustrative examples, we presented Ci(t) and Ce(t) calculated by the CFD method for various permeability-surface area products (PS), velocities, blood flows, ratios of the volume of the EVS to that of the IVS and lengths of the capillary. We also studied the effect of diffusion and the case when the PS changed depending on the axial position along the capillary. We concluded that the CFD method presented here will be useful for analysis of CA in the TH model, and it will contribute to a better understanding of the transcapillary exchange of CA.
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  • Yoshihiro ENOKIDO, Hiroyuki OKAMOTO, Yukio KIYOMIYA, Tomihisa FURUYA, ...
    2007 Volume 27 Issue 2 Pages 71-77
    Published: November 30, 2007
    Released on J-STAGE: September 24, 2012
    JOURNAL FREE ACCESS
    Field survey on output for X-ray therapeutic accelerators took place three times in Saitama Prefecture. The result of the field survey in 1997 showed the different rate from the designated dose at peak depth of 35 beams in 18 institutions. As different rate within ±-5% stood 91.4% in all beams, so different rate within ±3% stood 85.7% in the same beams. The average different rate from the designated dose at peak depth was +1706%. The standard deviation of the same condition was 3.72.
    The result of the field survey in 2005 showed the different rate from the designated dose at correction depth of 36 beams in 18 institutions. As different rate within ± 5% stood 100% in all beams, so different rate within ±3% stood 91.6% in the same beams. The average different rate from the designated dose at correction depth was +0.80%. The standard deviation of the same condition was 1.46.
    We und e rstood that the different rate from the designated dose at radiotherapeutic institutions decreased and even the value of the standard deviation was decreasing, by receiving 3 times of field surveys that was held in Saitama Pref. Also we understood that the beam numbers of different rate within ±5% and the beam numbers of different rate within ±3% were going up. We recognized that the good result of accurate dose is obtained more, by doing a continual field survey. The field survey was carried out in 2006 in Tochigi Prefecture and was the insufficient result in 10% of institutions.
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