非晶硅平板探测器（a-Si EPID）在放射治疗剂量验证中的应用研究

发布时间：2018-05-17 09:55

本文选题：非晶硅平板探测器 + 电子射野影像装置　；参考：《苏州大学》2013年硕士论文

【摘要】：非晶硅电子射野影像系统（amorphous silicon electronic portal imaging device，a-Si EPID）在加速器上应用非常广泛，主要是应用于图像引导治疗，以纠正摆位误差，在EPID发展过程中有不少学者致力于研究其在质控方面的应用潜力,如：平坦度和对称性分析、光野和射野一致性分析、半影分析、MLC位置验证和剂量验证等。其具有分辨率高、采集数据快、即时显示二维图像、抗辐射能力强、使用方便等优点，本课题建立在a-Si EPID成像基础上，研究其剂量验证功能，通过开发数据采集、剂量验证软件系统DVS(Dosimetric Verification System)，并对a-SiEPID进行一系列的校正，实现将影像转化为剂量分布。论文起始介绍了放疗剂量验证、常用设备以及EPID的发展历程，而后通过实验对a-Si EPID进行了初步的剂量学特性的分析，显示总体性能较好，但是使用常规泛野灵敏度校正方法，随射野离轴距离增大过反应效应增强。针对光子与a-SiEPID和水物理反应能力的差别，介绍了蒙特卡罗方法，并使用BEAMnrc程序包进行了Siemens Primus加速器、a-Si EPID和水模体的模拟、光子笔形束剂量沉积核的计算，，使用卷积方法将a-Si EPID光子通量转化为水中的通量，然后用模拟泛野的离轴比矩阵进行剂量分布校正与灰度-剂量校准后建立响应函数。在蒙卡模拟过程中同时分析了射野的相关特性，如光子和电子的能谱分布、离轴能量、离轴注量、辐射角等难以实际测量的物理项，以进一步加深对加速器的了解。针对临床上在剂量验证中常见的Gamma、剂量差(Dose Different, DD)和DTA分析法，设计实验对三种方法进行了优劣点的分析，最终在DVS软件采用Gamma分析法作为剂量验证的算法。随后使用a-Si EPID和MapCHECK分别采集一头部肿瘤的治疗计划，用各自软件分析，通过对比结果显示a-Si EPID的剂量验证应用具备可靠性，但是也呈现出一些问题需进一步研究解决。不过随着问题的解决，这将会促使a-Si EPID作为新的剂量验证设备的发展和应用。
[Abstract]:Amorphous silicon electronic portal imaging devicea-Si EPIDs are widely used in accelerators. They are mainly used in image-guided therapy to correct positioning errors. During the development of EPID, many scholars have devoted themselves to studying its application potential in quality control, such as flatness and symmetry analysis, optical field and field consistency analysis, penumbra analysis, position verification and dose verification, etc. It has the advantages of high resolution, fast data acquisition, real-time display of two-dimensional images, strong anti-radiation ability, convenient use and so on. This subject is based on a-Si EPID imaging, studies its dose verification function, and develops data acquisition. The dose verification software system DVS(Dosimetric Verification system, and a series of correction of a-SiEPID are carried out to transform the image into dose distribution. This paper first introduces the radiation dose verification, common equipment and the development history of EPID. Then, the dosimetric characteristics of a-Si EPID are analyzed through experiments. The results show that the overall performance is good, but the conventional pan-field sensitivity correction method is used. The overreaction effect increases with the off-axis distance of the field. In view of the difference between photons, a-SiEPID and hydrophysical reaction ability, Monte Carlo method is introduced, and the simulation of Siemens Primus accelerator, a-Si EPID and water motif, and the calculation of photon pen beam dose deposition nucleus are carried out by using BEAMnrc package. The a-Si EPID photon flux is converted to the flux in water by convolution method, and then the response function is established by using the off-axis ratio matrix of simulated panfield to correct the dose distribution and the gray-dose calibration. In the process of Monka simulation, the related properties of the emission field, such as the energy spectrum distribution of photon and electron, off-axis energy, off-axis beam, radiation angle, and so on, are analyzed simultaneously, so as to further understand the accelerator. In view of the Gamma, Dose difference (DDD) and DTA analysis, which are commonly used in clinical dose verification, the advantages and disadvantages of the three methods are analyzed in the design experiment. Finally, the Gamma analysis method is used as the dose verification algorithm in the DVS software. Then a-Si EPID and MapCHECK were used to collect the treatment plan of a head tumor. The results of comparison showed that the dose verification of a-Si EPID was reliable, but some problems needed to be solved. However, as the problem resolves, this will lead to the development and application of a-Si EPID as a new dose verification device.
【学位授予单位】：苏州大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：R144.1;TN36

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