本文選題：均整器　切入點：蒙特卡羅方法　出處：《南華大學(xué)》2012年碩士論文　論文類型：學(xué)位論文

【摘要】：在傳統(tǒng)的醫(yī)用直線加速器中，均整器是一重要的組成部分。X線經(jīng)過均整器后將原本不均勻的劑量分布修正成均勻的劑量分布，以滿足常規(guī)放療和三維適形放療的需求。調(diào)強放療中，優(yōu)化產(chǎn)生的注量分布一般是不均勻的，通過多葉準(zhǔn)直器(MLC)的運動可獲得治療所需要的注量。實際上，在這個過程中，MLC把加速器輸出的注量分布從均勻調(diào)制為不均勻。當(dāng)然，MLC也可以把加速器輸出的注量從固有的不均勻分布調(diào)制為調(diào)強所需的不均勻分布。為了讓加速器產(chǎn)生固有的不均勻分布，可以將均整器去除，但這可能對輸出射線的特性產(chǎn)生很大的影響，為此，，本論文對Varian Trilogy加速器6MV X線在有均整器(Flattening Filter,FF)和無均整器(Flattening Filter Free,FFF)條件下的劑量特性進行了蒙特卡羅模擬，探討均整器對劑量特性的影響。 本研究先用BEAMnrc和DOSXYZnrc分別模擬計算Varian Trilogy加速器6MV射線在具備均整器和去除均整器條件下，體積為50cm×50cm×50cm的均勻水體模中，方野邊長分別為1cm、2cm、3cm、4cm、6cm、8cm、10cm、12cm、15cm、20cm、30cm和40cm時的深度劑量（DD）和離軸比（OAR，最大劑量、5cm、10cm和20cm深度處）、總散射因子Sc,p和中心軸劑量比值，用BEAMDP分析光子能譜，然后對兩種條件下以上各物理量進行分析和比較。 研究結(jié)果表明無均整器條件下光子譜左移，射線質(zhì)變軟，光子通量增加；建成區(qū)深度劑量增加，建成區(qū)后深度劑量有一定幅度的降低；射野平坦度變差，射野越大越明顯；加速器輸出劑量率明顯增大；射野邊緣劑量減��；總散射因子Sc,p與射野的依賴關(guān)系相對變小。 總之，去除均整器后，加速器的輸出特性發(fā)生了明顯改變，臨床上可能產(chǎn)生一定的獲益或未知情況，尚需要進一步的研究支持。
[Abstract]:In the traditional medical linear accelerator, the integrator is an important component. After the X-ray is passed through the uniform device, the original uneven dose distribution is corrected into a uniform dose distribution. In order to meet the needs of conventional radiotherapy and three-dimensional conformal radiotherapy. In intensity modulated radiotherapy, the optimal dose distribution is generally uneven, and the dose required for treatment can be obtained through the motion of the MLC (multileaf collimator). In fact, In this process, MLC modulates the flux distribution of accelerator from uniform modulation to non-uniformity. MLC can also modulate the flux output from the inherent non-uniform distribution to the non-uniform distribution needed to adjust the intensity of the accelerator. The speeder produces an inherently uneven distribution, The integrator can be removed, but this may have a great influence on the characteristics of the output ray. In this paper, the dose characteristics of the Varian Trilogy accelerator 6MV X-ray under the condition of the FFF with the uniform device Flattening filter and the non-uniform Filter FFFF are simulated by Monte Carlo method. To investigate the effect of the integrator on the dose characteristics. In this study, BEAMnrc and DOSXYZnrc were used to simulate and calculate the 6 MV ray of Varian Trilogy accelerator in a uniform water model with 50 cm 脳 50 cm 脳 50 cm in volume under the condition of uniform device and removal of integral device, respectively. The side length of the square field is 1 cm, 2 cm, 3 cm, 3 cm, 6 cm, 6 cm, 8 cm, 10 cm, 12 cm, 15 cm, 20 cm, 20 cm, 30 cm and 40 cm depth. The depth dose (DDD) and off-axis ratio (Oar), maximum dose of 5 cm / 10 cm and 20cm depth, the ratio of total scattering factor scp to central axis dose, are analyzed by BEAMDP, and the energy spectra of photons are analyzed by BEAMDP. Then the above physical quantities under the two conditions are analyzed and compared. The results show that the photon spectrum shifts to the left, the ray quality becomes soft, the photon flux increases, the depth dose increases, the depth dose decreases to a certain extent, the field flattening becomes worse, the larger the field is, the more obvious the field is. The output dose rate of the accelerator is obviously increased, the edge dose of the projectile field decreases, and the dependence of the total scattering factor SCP on the ejection field is relatively small. In a word, the output characteristics of the accelerator have changed obviously after the whole device is removed, which may bring about some benefit or unknown situation in clinic, and need further research support.
【學(xué)位授予單位】：南華大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2012
【分類號】：TH774

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相關(guān)期刊論文 前1條

1 王志;鄔蒙;;調(diào)強放療中劑量率改變對生物效應(yīng)的影響[J];實用癌癥雜志;2007年05期

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