基于非晶硅平板探测器的剂量验证系统研究

发布时间：2018-04-09 01:14

本文选题：电子射野影像系统　切入点：非晶硅平板探测器　出处：《苏州大学》2012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）是目前最先进的射野影像工具，，其成像速度快、成像面积大、高分辨率、数字格式存储、耐受高剂量照射、快速获得二维平面剂量信息等优点，在加速器照射野常规质量控制的检测和放射治疗剂量学验证方面具有很大的优势。课题研究了a-Si EPID在加速器照射野常规质量保证和二维剂量验证的应用，使用C#语言研制了一套剂量验证系统软件,在计算照射野平坦度、对称性、半影、照射野和光野一致性以及二维剂量验证中显示出较高的实用性和较好的剂量精度。论文对非晶硅平板探测器的物理剂量学品质进行了研究，通过剂量刻度模式修正加速器均整器导致的射野不均匀性。将像素值转换为相对剂量分布得到不同照射野下的离轴比曲线，计算不同射野的平坦度、对称性和半影，并与三维水箱数据进行比较，分析所用的剂量刻度模式的可行性；通过计算射野中心到50%剂量线的距离与胶片测量结果进行比较，证明了a-Si EPID可以快速的用于照射野和光野一致性验证。在实现影像连续采集的基础上，对非晶硅平板探测器的剂量学特性进行了研究，分析各种参数的实际意义和相关影响因素，如稳定性、剂量线性、不同照射野大小的散射、帧时间、电容大小等。根据剂量线性响应关系拟合出剂量响应函数，将灰度图转化为射野剂量图。通过引入内散射校正模型，修正非晶硅平板探测器内部散射影响，设置规则和不规则野进行修正后的剂量验证实验。对TPS计划的RT dose数据解析，读取剂量图像；使用C#语言实现了Gamma分析法、距离一致性分析法和相对剂量差异法三种剂量比较算法，为TPS计算剂量分布与a-Si EPID实际测量的剂量分布比较提供了一种评估工具。
[Abstract]:The amorphous silicon electronic portal imaging devicesis-a-Si EPIDs are the most advanced image-field imaging tools at present. They have the advantages of fast imaging speed, large imaging area, high resolution, digital format storage and high dose tolerance.It has great advantages in conventional quality control of accelerator irradiation field and dosimetry verification of radiotherapy because of the advantages of fast obtaining two-dimensional planar dose information.The application of a-Si EPID in conventional quality assurance and two-dimensional dose verification of accelerator irradiation field is studied. A dose verification system software is developed by using C # language. The software is used to calculate the flatness, symmetry, penumbra and radiography of the irradiation field.The consistency of the radiation field and the light field as well as the two dimensional dose verification show higher practicability and better dose accuracy.The physical dosimetry quality of amorphous silicon flat panel detector is studied in this paper. The field heterogeneity caused by the accelerator homogenizer is corrected by the dose calibration mode.The off-axis ratio curves of different radiation fields are obtained by converting the pixel values into the relative dose distribution. The flatness, symmetry and penumbra of different radiation fields are calculated, and the feasibility of the dose calibration model is analyzed by comparing with the three-dimensional water tank data.By calculating the distance from the center of the field to the 50% dose line and comparing with the result of film measurement, it is proved that a-Si EPID can be used in the field of irradiation quickly.And field consistency verification.On the basis of continuous image acquisition, the dosimetric characteristics of amorphous silicon flat panel detector are studied. The practical significance of various parameters and related influencing factors, such as stability, dose linearity, scattering of different radiation fields, are analyzed.Frame time, capacitance size, etc.According to the dose linear response relation, the dose response function was fitted, and the gray scale image was transformed into the field dose map.By introducing the internal scattering correction model, the internal scattering effect of amorphous silicon flat detector is corrected, and the modified dose verification experiment is carried out by setting rules and irregular fields.The RT dose data of TPS program are analyzed and the dose images are read. Three dose comparison algorithms, Gamma analysis, distance consistency analysis and relative dose difference method, are implemented in C # language.This paper provides an evaluation tool for the comparison between the calculated dose distribution of TPS and the dose distribution measured by a-Si EPID.
【学位授予单位】：苏州大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH774

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