论文部分内容阅读
目的建立一种反向投影算法(模型),由射野影像和患者的CT图像,计算体内的三维剂量分布,进行剂量验证。方法该模型计算体内剂量分布步骤如下：(a)使用电子射野影像系统获取射野影像,将射野影像转换为射出剂量；(b)从射出剂量分布重建入射原射线注量分布；(c)由患者的三维信息(CT图像),计算得到体内的原射线剂量分布；(d)体内散射核叠加,求出体内散射线剂量分布,与原射线剂量相加,即得到体内的剂量分布。使用C语言编程实现算法。通过设置规则、不规则及调强射野,对均匀和不均匀、规则和不规则5种模体进行剂量验证实验,并将计算结果与测量结果进行比较。结果所有实验在射野内、剂量梯度小的区域计算的剂量和测量的剂量的偏差＜5%。在射野边界附近低密度肺组织内的计算剂量和测量的剂量的偏差＞5%。结论所建立的反向投影模型用于剂量验证,其准确性可满足临床要求。但模型还需进一步完善,以准确计算电子失平衡区的剂量。
Objective To establish a reverse projection algorithm (model) to calculate the three-dimensional dose distribution in the body from the radiographic images and the CT images of patients for dose verification. Methods The model calculates the dose distribution in the body as follows: (a) Transmitted field images are acquired using an electronic field imaging system and the radiation field images are converted to the emitted dose; (b) Reconstruction of the original radiation fluence distribution from the emitted dose distribution; (c) ) From the patient’s three-dimensional information (CT images), calculate the body’s original radiation dose distribution; (d) In vivo scattering nucleus superposition, calculate the in vivo scattered dose distribution, and the original radiation dose, that is, the body’s dose distribution. Using C language programming algorithm. By setting rules, irregularities and intensity-modulated fields, the dose-validation experiments on five kinds of motifs, uniform and inhomogeneous, regular and irregular, were carried out and the calculated results were compared with the measured results. Results All experiments deviated by <5% between the dose calculated in the dose field and the dose measured in the field with small dose gradients. The calculated and measured dose deviations> 5% in low-density lung tissue near the perimeter of the field. Conclusion The reverse projection model established for dose verification, its accuracy to meet the clinical requirements. However, the model needs to be further refined to accurately calculate the dose in the electronic imbalance zone.