数字化X射线摄影所致受检者辐射剂量估算研究

发布时间：2018-05-18 16:20

本文选题：数字化X射线摄影 + 剂量指示值　；参考：《复旦大学》2013年硕士论文

【摘要】：[目的]在医用X射线诊断中,数字化X射线摄影已逐渐取代传统的屏片式X射线摄影。本课题旨在通过研究数字化X射线摄影装置中的剂量指示值与受检者入射体表剂量、器官剂量和全身有效剂量之间的定量关系,建立用于快速估算数字化X射线摄影中受检者剂量的模式与方法,为开展医疗照射的剂量调查与集体剂量评估提供有效手段。 [方法]基于数字化X射线摄影(CR)装置中的剂量指示值,提出数字化X射线摄影中受检者入射体表剂量估算的理论模型,进一步重点探讨CR系统中管电压、总滤过和受检部位体厚这三个因素对估算模型的影响,建立剂量指示值与受检者入射体表剂量之间的定量关系模式；通过水模体实验测量和蒙特卡罗模拟计算确定模型中包括体厚衰减函数和成像板能量响应在内的相关参数。模型的普适性验证在三台X射线发生装置不同的摄影系统上进行,主要运用热释光剂量元件测量腹部正位摄影中受检者入射体表剂量；此外,还将本研究所建立的剂量指示值模型与曝光参数法、剂量面积乘积法比较,对比不同估算模式之间的差异。运用最新版本的MIRD数学模型和蒙特卡罗模拟计算软件MCNP5,开展受检者器官剂量和有效剂量的模拟计算,以取得不同摄影检查、不同管电压、不同总滤过条件下,受检者入射体表剂量-器官剂量的转换因子；并通过与已有入射体表剂量-器官剂量转换因子的比较,验证本研究所得转换因子的有效性。在此转换因子的基础上,结合最新的组织权重因子,进一步计算受检者的有效剂量,得出入射体表剂量-有效剂量的转换因子。最后,结合本研究所建立的入射体表剂量估算模型和入射体表剂量-有效剂量转换因子,给出通过剂量指示值估算有效剂量的方法。 [结果]本研究建立了利用剂量指示值估算数字化X射线摄影所致受检者入射体表剂量和有效剂量的数学模式。验证实验结果表明,利用本研究建立的方法估算得到的受检者入射体表剂量与实际测量值的相对偏差介于-16.9%到至18.1%之间,且该方法的估算值与其他方法的计算结果也相近。本研究计算得到的入射体表剂量与器官剂量的转换因子,对主射线束内器官而言与已有文献报道值的相对偏差在-28.6%到24.8%之间。在组织权重因子相同的条件下,本研究所得出的入射体表剂量与有效剂量的转换因子与已有文献报道值相对偏差在-12.5%到3.2%之间,两者吻合良好。 [结论]本研究所建立的数字化X射线摄影所致受检者剂量估算模式的计算结果,基本能满足辐射防护剂量学评价的精度要求。该估算模式可借助剂量指示值,管电压及受检部位厚度,直接估算某类数字化X射线摄影检查中受检者的入射体表剂量、主要器官的吸收剂量和全身有效剂量。可为数字化X射线诊断中受检者剂量的现状或回顾性调查提供了一种便捷且有效的方法与手段。
[Abstract]:Objective: in medical X-ray diagnosis, digital X-ray photography has gradually replaced the traditional screen-type X-ray photography. The purpose of this paper is to study the quantitative relationship between the dose indication value in the digital X-ray camera and the incident surface dose, organ dose and the effective dose of the whole body. To establish a model and method for rapid estimation of dose of subjects in digital X-ray photography, and to provide an effective means for carrying out dose investigation and collective dose assessment of medical exposure. [methods] based on the dose indication in the digital X-ray radiography system, a theoretical model for estimating the incident dose of the person tested in digital X-ray photography is proposed, and the tube voltage in the CR system is further discussed. The influence of three factors, total filtration and body thickness, on the estimation of the model, and the quantitative relationship between the dose indicator and the incident dose of the body surface were established. The parameters of the model including the attenuation function of body thickness and the energy response of the imaging plate are determined by the measurement of the water model and the Monte Carlo simulation. The universal validation of the model is carried out on three different radiographic systems. The thermoluminescence dose elements are mainly used to measure the incident surface dose of the subjects in orthotopic abdominal photography. The dose indicator model is compared with the exposure parameter method and the dose area product method, and the differences between different estimation models are compared. The latest version of MIRD mathematical model and Monte Carlo simulation software MCNP5 are used to simulate and calculate organ dose and effective dose in order to obtain different photographic examination, different tube voltage and different total filtering conditions. The conversion factor of incident surface dose to organ dose is verified by comparing with the existing incident surface dose-organ dose conversion factor. On the basis of this conversion factor and the latest tissue weight factor, the effective dose of the subject is further calculated, and the conversion factor between the incident surface dose and the effective dose is obtained. Finally, a method to estimate the effective dose through the dose indication is given, which is based on the incident surface dose estimation model and the incident surface dosis-effective dose conversion factor. [results] A mathematical model was established to estimate the incident dose and effective dose of the subjects induced by digital X-ray photography. The experimental results show that the relative deviation between the estimated incident dose and the actual measured value is between -16.9% and 18.1%, and the estimated value of this method is similar to that of other methods. In this study, the relative deviation between the incident body surface dose and the organ dose was -28.6% to 24.8% for the organs in the main ray beam. Under the condition of the same tissue weight factor, the relative deviation between the incident surface dose and the effective dose is -12.5% to 3.2%, which is in good agreement with the reported values. [conclusion] the calculated results of the dose estimation model established by this study can basically meet the requirements of radiation protection dosimetry evaluation. With the aid of dose indication, tube voltage and site thickness, the model can directly estimate the incident body surface dose, the absorbed dose of the main organs and the effective dose of the whole body in a kind of digital X-ray examination. It can provide a convenient and effective method for the present situation or retrospective investigation of dose in digital X-ray diagnosis.
【学位授予单位】：复旦大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：R814.2

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