| Project/Area Number |
20591501
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Radiation science
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| Research Institution | Nagoya City University |
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Principal Investigator |
SHIBAMOTO Yuta Nagoya City University, 大学院・医学研究科, 教授 (20144719)
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| Co-Investigator(Kenkyū-buntansha) |
ITO Masato 名古屋市立大学, 大学院・医学研究科, 准教授 (20244569)
MURATA Rumi 名古屋市立大学, 大学院・医学研究科, 講師 (10444960)
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| Project Period (FY) |
2008 – 2010
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| Project Status |
Completed (Fiscal Year 2010)
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| Budget Amount *help |
¥3,770,000 (Direct Cost: ¥2,900,000、Indirect Cost: ¥870,000)
Fiscal Year 2010: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2009: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Fiscal Year 2008: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
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| Keywords | 定位照射 / 放射線治療生物学 / LQモデル / 分割照射 / 線量換算 |
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| Research Abstract |
The reliability of the linear-quadratic (LQ) formalism in assessing biological equivalence between single high and hypofractionated radiation doses were investigated using single cells, spheroids and murine tumors. Single doses of 2-26Gy and 2-5 fractions of 4-12Gy were used. The α/β ratio was obtained from the cell survival curves, and using it and the LQ formalism, equivalent single doses for the hypofractionated doses were calculated. They were then compared with actually-determined equivalent single doses for the hypofractionated doses. In all experiments, equivalent single doses for hypofractionated doses calculated from the LQ formalism were lower than the actually-measured biologically-equivalent single doses by 10-40%. Conversion of hypofractionated radiation doses to single doses using the LQ formalism underestimated the effect of hypofractionated radiation. In direct comparison of the 2- to 5-fraction schedules, respective dose-response curves almost overlapped when cell survival was plotted against actual radiation doses. However, the curves tended to shift downwards by increasing the fraction number when cell survival was plotted against biologically effective doses (BED) calculated using an α/β ratio for in vitro EMT6 cells. Thus, BED was inappropriate. Using the multi-target model, the compatibility improved at high doses, but still dose conversion was not perfect. Other biological models are now being investigated.
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