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題名 | 常用劑量計在強度調控放射治療劑量驗證之應用劑量驗證=The Applications of Routine Dosimeters in IMRT Dose Verification |
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作者 | 溫嘉綺; 陳信雄; 黃英強; 賴源淳; 劉幕台; | 書刊名 | 臺灣應用輻射與同位素雜誌 |
卷期 | 2:4 民95.12 |
頁次 | 頁211-219 |
分類號 | 416.36 |
關鍵詞 | 劑量驗證; 強度調控放射治療; 游離腔; 熱發光劑量計; Dose verification; Intensity modulated radiotherapy; Ion chamber; TLD; |
語文 | 中文(Chinese) |
中文摘要 | 強度調控放射治療,其基本原理爲使用非均勻的射束強度,加上劑量堆疊的概念,使劑量能順著腫瘤的形狀分布。因此在劑量分布上容易有較大的劑量梯度產生,因而造成劑量驗證的困難。本研究採用的劑量驗證方式是使用兩種不同的假體:固態假體(solid water phantom)與擬人假體(Rando phantom)。另外,使用不同的劑量計:兩種不同體積大小的游離腔用於評估參考點之絕對劑量;以及使用熱發光劑量計置入擬人假體中以取得不均質假體劑量驗證的資訊,且經由多處佈點在單次照射中即可取得多處離軸點劑量表現。最後將劑量測量值與治療計畫之計算值相比,作爲劑量驗證的依據。將電腦治療計畫和測量值比對結果顯示:游離腔在劑量梯度平坦處,不論是中心點或是離軸點其絕對劑量差異均在2%內:TLD在靠近中心點的絕對劑量差異也在3%內。從研究結果顯示,得到以下結論:游離腔是提供單點劑量驗證的最佳劑量計;TLD也可用來作爲量測工具,但是TLD本身變異性較大,且體積小,在測量點中過大的可移動空間,增加了誤差的來源。 |
英文摘要 | The basic principle for Intensity Modulated radiotherapy (IMRT) is using non-uniform beam intensity and "dose accumulation" concept to make the dose distibutions "conform" the tumor volume. The dose distribution will show a great dose gradient. This high dose gradient makes dose measurement more difficult. We applied two different types of phantom for our sway; solid water phantom and rando phantom. Besides the phantom, we used various dosimeters for our dose measurements; two different sizes ion chambers or absolute dose measurements and TLD for inhomogeneous phantom measurement and for off-axis dose measurements. The results of comparing calculation o treatment planning system with measurements stow the followings: The differences in absolute dose at flat dose gradient area, either at the center or at the off-axis points, are all within 2% with ion chamber measurements; The absolute dose nearby the center has a difference less than 3% with TLD dosimetry. From the results of our study, we conclude: The ion chamber is the best tool for absolute dose verification: TLD is also a good tool for does measurements. But the higher dose response variation and the difficulty in position accuracy increase the source of error in TLD dosimetry. |
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