基于锥形束CT研究肺癌图像引导放疗的内靶区外放边界值

目的：研究肺癌锥形束CT图像引导放疗联合在线配准方式的内靶区外放边界。方法：选取24例肺癌患者，应用医科达Synergy加速器行CBCT扫描，将获取的CBCT图像与计划4DCT图像配准，得到患者放疗时三维方向上的平移摆位误差和旋转误差，XVI系统配合治疗床进行在线校正，并计算内靶区外放边界值。结果：24例患者共行380次CBCT扫描，校正前后：左右、头脚、前后方向的外放值M分别为5．3mm、8．6mm、3．8mm和2．2mm、1．8mm、1．1mm。校正前后旋转误差数据结果显示，RⅣ、R），轴向上有统计学意义（t=2．817，P=-0．005；产一3．481，P=0．001），Rz轴上差异无统计学意义（t=0．554，P=0．580）。结论：肺癌患者采用CBCT下图像引导放疗可显著缩小ITV外放范围，提高放疗精度，有效降低正常组织受照射范围，提升肿瘤放疗剂量，弥补手术局部复发率高的劣势。

Research of Defining an ITV to PTV Margins for Lung Carcinoma Based on Cone-beam CT Image Guided Radiotherapy

Abstract：Objective：To study the appropriate margins for internal target volume （ITV） using cone-beam CT （CBCT） image guided radiation therapy combined with online registration method for lung carcinoma.Methods：Twenty-four patients with lung carcinoma were investigated. Elekta Synergy linac was applied to acquire KV CBCT scans and image registration was achieved by the acquired CBCT images vs planning 4D-CT.Each set of translation setup errors and rotation errors in three-dimensional direction were recorded and analyzed.Before the irradiation,online correction was implemented on the treatment bed via XVI system.The ITV translation margins were calculated before and after correction.Results：Totally,380 datasets of CBCT images from 24 patients were analyzed.Before non-correction,the margins required to consider for systemic and random error were 5.3 mm、8.6 mm、3.8 mm in left-right,superior-inferior and anteriorposterior directions.After the intrafraction setup errors were considered and corrected,margins were 2.2 mm、1.8 ram、1.1 mm,respectively.According to the results of rotation errors before and aider correction,data was statistically significant in Rx and Ry axis（t = 2.817, P = 0.005; t = 3.481, P = 0.001）.But there was no change in Rz axis（t = 0.554, P = 0.554）.Conclusions： CBCT image guided radiation therapy with lung carcinoma can significantly reduce the ITV margin scope,improve the precision of radiotherapy, effectively reduce the scope of normal tissue irradiated, promote tumor radiotherapy dose, make up for surgery disadvantage of local recurrence.