基于EPID三维剂量重建在肿瘤患者中应用

Application of EPID-based 3D dose reconstruction in cancer patients

目的 基于EPID利用Edose软件重建三维剂量分布,帮助放疗工作人员更好地了解治疗期间患者相关危及器官和靶区的剂量变化情况。方法 对头颈部肿瘤和胸部肿瘤患者治疗前行1 次/周总共6次CBCT扫描,将CBCT图像与计划CT图像进行刚性配准后传入到Edose剂量分析软件中,利用Edose软件根据摆位误差基于EPID对其进行三维剂量重建,最后分析不同危及器官剂量并比较γ通过率。结果 与原计划剂量相比,鼻咽癌患者脊髓Dmax分次间受量波动较大且高于患者原计划剂量,脑干Dmax分次间受量变化较小,左右腮腺V30所受剂量变化较大,单次增加幅度最高可达28.69%;胸部肿瘤患者脊髓Dmax差异较小,肺与心脏实际受量都高于计划剂量,尤其肺V5与原计划平均偏差达16.99%（P〈0.05）。通过对γ通过率分析可看出危及器官受量与原计划受量存在较大变化的节点为头颈部肿瘤第16次左右和胸部肿瘤第24次左右。结论 通过在单次治疗中利用Edose剂量验证系统基于EPID重建患者体内三维剂量的分布,可以了解相关靶区与危及器官的剂量变化,能够更好地保护危及器官以及提高靶区剂量的覆盖率,为下一步的剂量引导放射治疗和自适应放射治疗提供一定的参考。

Objective To perform 3D dose reconstruction based on electronic portal imaging device （EPID） of linear accelerator for the static intensity-modulated using Edose,a dose verification system, Aiming to assist the radiotherapy professionals to better understand the radiotherapy organs at risk and target dose changes. Methods CBCT image was acquired for patients with head and neck cancer and thoracic cancer once a week for a total of six times. Subsequently,CBCT images and planning CT images were subject to rigid registration and exported to the Edose software. According to the setup error,EPID-based three-dimensional dose reconstruction was performed by using Edose software. The gamma passing rate and dose of different organs at risk （OARs） were analyzed and statistically compared. Results For patients with nasopharyngeal carcinoma,the intra-fractional Dmax of the spinal cord was more significantly fluctuated and higher compared with the planning dose,whereas the intra-fractional Dmax of the brainstem did not significantly fluctuate. The V30 of the parotid gland significantly changed with a maximum increase of 28.69% per fraction. For patients with thoracic tumors,the Dmax of the spinal cord was slightly changed,and the actual doses in the lung and heart were higher than the planning doses. The average deviation of the pulmonary V5 was up to 16.99% between the actual and planning doses with statistical significance （P〈0.05）.According to the analysis of gamma passing rate,significant dose changes occurring in the OARs were detected in the 16^th fraction for the head and neck cancer and the 24^th fraction for the thoracic neoplasms. Conclusions The dose changes in the OARs can be obtained by reconstructing the EPID-based 3D dose distribution using the Edose software for each fraction,which can better protect the OAR,enhance the coverage of target dose and provide certain reference for dose-guided and self-adaptive radiotherapy.