【摘要】：自質(zhì)子治療概念提出以來,質(zhì)子放療技術(shù)得到了廣泛的關(guān)注并迅速地發(fā)展。精確放療是當前的主流方向,其中“精確定位”的實現(xiàn)是精確放療的良好開端,被更多的研究者所關(guān)注。目前,對靶區(qū)定位的在線監(jiān)測一般采用湮滅伽馬射線成像的方式。然而這種方式的定位偏差在幾毫米甚至到厘米量級,誤差較大,因此對“精確定位”提出了更高要求。近年來蒙特卡羅方法已成為醫(yī)學研究中方案設(shè)計及優(yōu)化的一種最常用手段,本文利用此方法對質(zhì)子治療中產(chǎn)生的湮滅光子進行圖像重建,提出一種新的定位方式,極大地提高了定位的精準度。質(zhì)子與人體中~(16)O反應(yīng)生成正電子核素13N,衰變后釋放的正電子與體內(nèi)電子發(fā)生湮滅反應(yīng)生成光子。通過追蹤光子的位置和質(zhì)子在路徑上的能量沉積這兩個信息進行靶區(qū)定位。本文利用MCNPX程序進行建模計算,模擬了能量為60 MeV-150 Me V的質(zhì)子束在肌肉組織中的輸運及能量為90 Me V的質(zhì)子束在不同材料的GTV(腫瘤靶區(qū))中的輸運,討論分析了質(zhì)子入射能量及GTV材料對湮滅光子分布的影響。提出“湮滅光子峰”概念,定義湮滅光子通量下降梯度最大的位置為湮滅光子峰位置。重建湮滅光子通量一階導數(shù)的圖像,評估峰位置,模擬結(jié)果顯示湮滅光子峰位置與Bragg峰位置相差無幾,位置偏差小于1 mm,定位精準度高。本工作在驗證新定位方式可行性的同時也為后續(xù)精準定位的研究提供了參考數(shù)據(jù)。
[Abstract]:Since the concept of proton therapy was put forward, proton radiotherapy technology has been widely concerned and developed rapidly. Accurate radiotherapy is the mainstream direction at present, and the realization of accurate positioning is a good beginning of accurate radiotherapy, which has been paid more attention by researchers. At present, annihilation gamma-ray imaging is generally used to monitor the target location on-line. However, the positioning deviation of this way is in the order of several millimeters or even to centimeters, and the error is large, so the "accurate positioning" is required higher. In recent years, Monte Carlo method has become one of the most commonly used methods in the design and optimization of medical schemes. In this paper, we use this method to reconstruct the image of annihilation photons produced in proton therapy, and propose a new localization method. The accuracy of positioning is greatly improved. Proton reacts with ~ (16) O to form positron 13N, and the released positron is annihilated with in vivo electrons to form photons. The target is located by tracking the position of the photon and the energy deposition of the proton on the path. In this paper, the transport of proton beam with energy of 60 MeV-150 Me V in muscle tissue and proton beam with energy of 90 Me V in GTV (tumor target region) of different materials are simulated by MCNPX program. The effects of proton incident energy and GTV material on the annihilation photon distribution are discussed and analyzed. The concept of "annihilation photon peak" is put forward, and the position of annihilation photon peak is defined as the position where the maximum drop gradient of annihilation photon flux is obtained. The image of the first derivative of annihilation photon flux is reconstructed and the peak position is evaluated. The simulation results show that the position of the annihilation photon peak is almost the same as that of the Bragg peak, and the position deviation is less than 1 mm,. This work not only verifies the feasibility of the new positioning method, but also provides reference data for the further research of precise positioning.
【學位授予單位】：吉林大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：R815

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