Methods of improving the accuracy of high-energy X-ray absorbed dose calculated using a convolution approach

使用直线加速器产生4 mV、10 mV和15 mV X射线的三能束。1.在X射线强度透射率数据的基础上，提出了一种估算X射线能谱的方法，并编制了相应的计算程序。在这种情况下，使用楔形板和补偿器引起的初级X射线光谱变化可以很容易地准确地评估，并且可以很容易地准确地评估受照射物体内的初级X射线光谱变化：因此，现在可以进行更准确的剂量计算。2.在X射线光谱的基础上，将水中衰减系数表示为深度的函数，然后推导出零面积组织最大比(TIR)。利用零面积TMR公式中的一些常数来构造初级和散射剂量扩散函数。3.利用水和三层CO-…测量了组织-模体比(TPR几个照射场的更多RK模体。还使用水和三层软木模体测量了几个照射区域的剂量OCR(偏心比)。这些数据被用来重新确认使用卷积方法进行剂量计算的基本函数，如初级剂量扩展函数、散射剂量扩展函数、污染电子强度函数和准直器OCR函数。4.引入准直器OCR的概念来评估由于一对上下颌骨而产生的屏蔽效应。还引入了“源OCR”的概念，用于计算无限远场的入射X射线强度。提出了用准直器OCR函数和源OCR函数的乘积来表示有限场某一点的入射X射线强度。5.提出了一种剂量计算方法，将多叶准直器(MLC)、楔形体、屏蔽块和床层视为受照体的一部分。6.利用初级和散射剂量扩散函数表达式可以解析积分的特点，尝试了3D剂量计算软件的加速。较少

Using a linear accelerator producing triplet-energy beams of 4-, 10-, and 15-MV X-rays. the following experimental and theoretical studies were performed.1.On the basis of X-ray intensity transmission data, we developed a method to estimate X-ray spectra and then constructed its calculation program. Under this situation, the primary X-ray spectrum variation caused by using wedges and compensators can be easily evaluated with accuracy and the primary X-ray spectrum variation within an irradiated body can also be easily evaluated with accuracy : Therefore, more accurate dose calculations can now be performed.2.On the basis of the X-ray spectrum, the in-water attenuation coefficient was expressed as a function of depth, and then the zero-area tissue-maximum ratio (TIR) was formulated. Some of the constants in the zero-area TMR formulation were utilized for constructing primary and scatter dose spread functions.3.Sets of tissue-phantom ratios (TPRs) were measured using water and 3-layed co … More rk phantoms for several irradiation fields. Sets of dose OCRs (off-center ratios) were also measured using water and 3-layed cork phantoms for several irradiation fields. These sets of data were utilized to reconfirm such fundamental functions, for dose calculation using a convolution method, as primary-dose spread functions, scatter-dose spread functions, contaminant electron intensity functions, and collimator OCR functions.4.The concept of "collimator OCR" was introduced for evaluation of the shielding effect due to a pair of lower and upper jaws. The concept of "source OCR" was also introduced for evaluation of the incident X-ray intensity at an infinite field. It was proposed that the incident X-ray intensity at a point for a finite field was expressed as the product of the collimator OCR and source OCR functions.5.A dose calculation approach was proposed to regard the multi-leaf collimator (MLC), the wedge, the shielding blocks, and the couch as parts of an irradiated body.6.Speeding Up of the 3D dose calculation soft was attempted by utilizing the fact that both primary and scatter dose spread functional expressions could be integrated analytically. Less