Estimation of High-Energy Primary Photon-Induced Doses for Non Charged Particle Equilibrium Conditions

帶電粒子不平衡狀態下之高量光子劑量的評估

趙敏(Max M. Chao) ； George E. Chabot

《放射治療與腫瘤學》 2卷1期 (1995/03) Pp. 47-55

https://doi.org/10.6316/TRO/199502(1)47

摘要

當一束高能量的光子照射到－物質上時，通常在臨接於物質表面下的一小部份區域內所產生的電子，並不會達到－平衡穩定的狀態。本研究計劃利用所導出來的次級電子能量分佈曲線方程式來計算在不同光子能量射束下的次級電子分佈曲線情形，再以所產生的次級電子能量光譜加上SPencer的電子在物質中之能量消散分佈曲線數據，來推算在增建區域內從皮膚表面到極大劑量Dmax下之光子劑量，最後以所得到的增建區域內光子劑量分佈曲線數據推演出一個以自然指數為底的方程式，來代表不同能量的光子在增建區域內之劑量分佈曲線情形。所計算的光子能量從鈷六十的1.25 MeV（百萬電子伏特）到25 MV的直線加速器等。

關鍵字

光子劑量 ； 增建劑量

並列摘要

This research used derived equations for secondary electron energy distributions in water irradiated by gamma rays in conjunction with generated electron spectra for different incident photon energies to estimate primary photon-induced absorbed doses for non charged particle equilibrium conditions in the dose buildup regions. The pair production contribution was added to the Compton spectrum for 2 MeV to 30 MeV photons. The generated electron spectral data were combined with Spencer's electron energy dissipation distribution data to calculate the buildup dose from the skin surface up to the depth of maximum dose under non charged particle equilibrium conditions. We then fit our calculated results to exponential and polynomial forms and obtained the final buildup dose in one exponential form. The computed results for 1.25 MeV, 5 MeV and 10 MeV monoenergetic photons are presented and compared to experimental results for (superscript 60)Co gamma radiation, and 10 MV and 25 MV accelerator produced radiations.

並列關鍵字

Photon dose ； Buildup dose