A sector-integration method for dose/MU calculation in a uniform scanning proton beam.
A sector-integration method for dose/MU calculation in a uniform scanning proton beam.
复制标题
均匀扫描质子束中剂量/MU 计算的扇区积分方法。
DOI：
10.1088/0031-9155/55/3/n02
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发表时间：
2010
影响因子：
3.5
通讯作者：
Das,IndraJ
中科院分区：
文献类型：
--
作者：
Zhao,Qingya;Wu,Huanmei;Wolanski,Mark;Pack,Daniel;Johnstone,PeterAS;Das,IndraJ
本文提出了一种精确、简便、省时的扇形积分方法，用于计算质子输出量（剂量/监测单位，MU），该方法基于以下治疗野参数：孔径形状、孔径大小、测量位置、射束范围和射束调制。该模型是验证与剂量/MU值为431字段先前在我们的中心测量。测量是在水模中用平行板电离室均匀扫描质子束获得的。对于临床感兴趣的射束穿透深度（6-27 cm水），测量剂量/MU值作为扩展布拉格峰（SOBP）范围和孔径直径的函数。首先，使用90个随机选择的射野推导模型参数，这些参数用于计算剩余341个射野的剂量/MU值。对于不同的能量范围、孔径尺寸、测量位置和SOBP值，使用341个射野的计算和测量剂量/MU值之间的差值的最小值、最大值、平均值和标准差来评价准确度和稳定性。对5种不同函数集的实验结果表明，该计算模型具有较高的精度，计算误差在-2.4%~3.3%之间，99%的误差小于± 2%。随着能量的增加、SOBP的增大和孔径的增大，测量精度也随之提高。小野（野大小< 25 cm 2）剂量/MU计算的平均误差为0.31±0.96（%）。
An accurate, simple and time-saving sector integration method for calculating the proton output (dose/monitor unit, MU) is presented based on the following treatment field parameters: aperture shape, aperture size, measuring position, beam range and beam modulation. The model is validated with dose/MU values for 431 fields previously measured at our center. The measurements were obtained in a uniform scanning proton beam with a parallel plate ionization chamber in a water phantom. For beam penetration depths of clinical interest (6–27 cm water), dose/MU values were measured as a function of spread-out Bragg peak (SOBP) extent and aperture diameter. First, 90 randomly selected fields were used to derive the model parameters, which were used to compute the dose/MU values for the remaining 341 fields. The min, max, average and the standard deviation of the difference between the calculated and the measured dose/MU values of the 341 fields were used to evaluate the accuracy and stability, for different energy ranges, aperture sizes, measurement positions and SOBP values. The experimental results of the five different functional sets showed that the calculation model is accurate with calculation errors ranging from− 2.4% to 3.3%, and 99% of the errors are less than±2%. The accuracy increases with higher energy, larger SOBP and bigger aperture size. The average error in the dose/MU calculation for small fields (field size< 25 cm 2) is 0.31±0.96 (%).