Predictive gamma passing rate by dose uncertainty potential accumulation model
Predictive gamma passing rate by dose uncertainty potential accumulation model
复制标题
通过剂量不确定性潜在累积模型预测伽玛通过率
DOI：
10.1002/mp.13333
复制
发表时间：
2019
期刊：
影响因子：
3.8
通讯作者：
Y. Nagata
中科院分区：
文献类型：
--
作者：
E. Shiba;A. Saito;Makoto Furumi;Y. Murakami;T. Ohguri;M. Tsuneda;K. Yahara;T. Nishio;Y. Korogi;Y. Nagata
目的
调强放射治疗（IMRT）利用许多小野来产生均匀的剂量分布。因此，在目标区域中存在许多场结，并且由此产生的剂量不确定性被累积。然而，这种累积的剂量不确定性还没有实现在目前的实践中的IMRT剂量验证。本研究的目的是开发一种方法来预测的γ通过率（GPR）使用剂量不确定性累积模型。
方法
在这项研究中使用了33个强度调制（IM）光束的头部和颈部的情况下，与步骤和拍摄技术。使用XiO治疗计划系统（TPS）创建治疗计划。IM射束由ONCOR Impression Plus直线加速器产生。使用Maplitazone测量剂量分布。剂量不确定性电位（DUP）的分布由内部软件生成，该软件通过分段监测单元加权累积射野形状，然后进行高斯折叠。高斯的宽度由外侧半影的宽度确定。将计算剂量和测量剂量之间的剂量差异与每个点的估计DUP进行比较。每个光束的GPR预测为2%/2-mm，3%/2-mm，和3%/3-mm的公差通过其自己的DUP直方图和GPR与DUP的相关性的其他光束使用留一交叉验证方法。将预测的探地雷达与实测的探地雷达进行了比较，以评价该预测方法的性能。为了验证该方法用于估计探地雷达实测值的可行性，提出了探地雷达实测值≥ 90%的判据。
结果
证实DUP与剂量差异的标准差（SD）成比例。对于2%/2 mm、3%/2 mm和3%/3 mm公差，测量和预测GPR之间差异的SD分别为3.1、1.7和1.4%。对应于实测GPR ≥ 90%的预测GPR标准分别为94.1%和95.0%，置信水平分别为99%和99.9%。
结论
在本研究中，我们证实了剂量差异与估计DUP之间的良好比例关系。结果表明，根据DUP蓄积模型估计，预测DUP的剂量差异是可行的。在这项研究中开发的预测GPR显示了良好的准确性，头部和颈部IMRT的平面剂量分布。在这项研究中开发的预测方法被认为是可行的，作为目前的实践的测量为基础的验证剂量分布与伽马分析的替代。
PURPOSE
Intensity-modulated radiation therapy (IMRT) utilizes many small fields for producing a uniform dose distribution. Therefore, there are many field junctions in the target region, and resulting dose uncertainties are accumulated. However, such accumulation of the dose uncertainty has not been implemented in the current practice of IMRT dose verification. The purpose of this study is to develop a method to predict the gamma passing rate (GPR) using a dose uncertainty accumulation model.
METHODS
Thirty-three intensity-modulated (IM) beams for head-and-neck cases with step-and-shoot techniques were used in this study. The treatment plan was created using the XiO treatment planning system (TPS). The IM beam was produced by the ONCOR Impression Plus linear accelerator. MapCHECK was used to measure the dose distribution. The distribution of a dose uncertainty potential (DUP) was generated by in-house software that accumulated field shapes weighted by a segmental monitor unit, followed by Gaussian folding. The width of the Gaussian was determined from the width of the lateral penumbra. The dose difference between the calculated and measured doses was compared with the estimated DUP at each point. The GPR of each beam was predicted for 2%/2-mm, 3%/2-mm, and 3%/3-mm tolerances by its own DUP histogram and a GPR-vs-DUP correlation of other beams using the leave-one-out cross-validation method. The predicted GPR was compared with the measured GPR to evaluate the performance of this prediction method. The criteria for the predicted GPR corresponding to a measured GPR ≥ 90% were estimated to examine the feasibility of estimating the measured GPR by this GPR prediction method.
RESULTS
The DUP was confirmed to have proportionality to the standard deviation (SD) of the dose difference. The SDs of the difference between the measured and predicted GPRs were 3.1, 1.7, and 1.4% for 2%/2-mm, 3%/2-mm, and 3%/3-mm tolerances, respectively. The criteria of the predicted GPR corresponding to the measured GPR ≥ 90% were 94.1 and 95.0% with confidence levels of 99 and 99.9%, respectively.
CONCLUSION
In this study, we confirmed the good proportionality between the dose difference and the estimated DUP. The results showed a feasibility to predict the dose difference from DUP as estimated by a DUP accumulation model. The predicted GPR developed in this study showed good accuracy for planar dose distributions of head and neck IMRT. The prediction method developed in this study is considered to be feasible as a substitute for the current practice of measurement-based verification of the dose distribution with gamma analysis.