摘要:
在精确放射治疗中,精确计算楔形挡板的楔形因子是精确修正加入楔形挡板后剂量值的关键.提出了基于衰减系数法思想的改进楔形野剂量修正算法,首先计算了楔形挡板材料的线性衰减系数,再根据楔形挡板的实际剖面尺寸,建立了线性拟合公式计算射线束穿过楔形挡板的实际厚度,精确计算楔形因子,并以AAPM55号报告提供的45°楔形挡板进行了验证.该方法在保证计算精度的同时减少了大量离轴测量数据,减轻了物理师的负担,可以作为一种有效的楔形挡板修正算法应用于放射治疗计划系统中.
Abstract:
In accuracy radiotherapy,it is difficult to calculate dose accurately during wedge fields.In this paper,an improved corrected algorithm of wedges based on the line-attenuation was proposed.The line-attenuation coefficient of wedges was calculated firstly,then the actual path of radial beam in the wedge was calculated by the "linear fitting" according to the sizes of wedges section.Finally the wedge factors could be determined accurately,and the dose could be corrected.The data of the 45 degree wedge in the report of AAPM 55 were used to make the calculation and verificaton.Using this algorithm,amount of measured data were decreased,the accuracy of calculation could be assured,and the job of physician could be reduced,so this algorithm could be applied in the treatment planning system as an effective calculation method of wedges field.
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