Abstract：
Objective:The development of a stringent derivative-based gamma (DBG) index for patient-specific QA in stereotactic radiotherapy treatment planning (SRTP) to account for the spatial change in dose.Methods:Twenty-five patients of liver SBRT were selected retrospectively for this study. Deliberately, two different kinds of treatment planning approaches were used for each patient. Firstly, the treatment plans were generated using a conventional treatment planning (CTP) approach in which the target was covered with a homogeneous dose along with the nominal dose fall-off around the treatment field. Subsequently, the other treatment plans were generated using an SRTP approach with the intent of heterogeneous dose within the target region along with a steeper dose gradient outside the treatment field as much as possible. For both kinds of treatment plans, two dimensional (2D) conventional gamma (CG) and DBG analysis were performed using the 2D ion chamber array and radiochromic film.Results:Difference in the DBG index was statistically significant whereas, for CG analysis, the difference in CG index was insignificant for both types of treatment plans (CTP and SRTP). A significant positive correlation was observed between the difference in the DBG index and the difference in HI for high gamma criteria.Conclusion:The DBG evaluation is found to be more rigorous, and sensitive to the only SRTP. The proposed method could be opted-in the routine clinical practice in addition to CG.Advances in knowledge:DBG is more sensitive to detect the spatial change of dose, especially in high dose gradient regions.
摘要：
目标：在立体定向放射治疗计划（SRTP）中开发用于患者特定QA的严格的基于导数的伽马（DBG）指数，以考虑剂量的空间变化。方法:回顾性分析25例肝脏SBRT患者的临床资料。故意,对每位患者使用两种不同的治疗计划方法.首先,治疗计划是使用常规治疗计划(CTP)方法生成的,其中目标被均一剂量覆盖,治疗区域周围的标称剂量减少.随后，其他治疗计划是使用SRTP方法生成的,目的是在目标区域内使用异质剂量,同时尽可能在治疗区域外使用更陡的剂量梯度.对于这两种治疗方案，使用2D离子室阵列和放射变色膜进行二维（2D）常规伽马（CG）和DBG分析。结果:DBG指数差异有统计学意义,对于CG分析，两种治疗方案(CTP和SRTP)的CG指数差异均不显著.对于高伽马标准，DBG指数的差异与HI的差异之间存在显着的正相关。结论：DBG评估更严格，并且对唯一的SRTP敏感。除CG外，建议的方法还可以在常规临床实践中选择。知识进步：DBG对检测剂量的空间变化更敏感，特别是在高剂量梯度区域。
