靶区中心平均位置在肺部三维适形放疗中的应用

目的：探讨靶区中心的平均位置应用于肺部三维适形放射治疗的可行性。方法：选取可接受三维适形放射治疗的周围型肺癌患者8例，在治疗体位和自由呼吸的情况下，应用多序列时相特异性快速CT扫描技术进行扫描。扫描图像传输到三维治疗计划系统后，按序列进行三维重建，计算各序列肿瘤中心坐标，求出靶区中心的平均位置。制定治疗计划时将照射野中心置于靶区中心的平均位置，计算靶体积，并于放射治疗前和过程中应用电子射野影像系统进行验证，并与靶区中心平均位置法的靶体积进行比较。结果：按靶区中心平均位置方法计算出的靶体积与GTV外放10mm和20mm的靶体积相比，平均靶区中心法的靶体积显著减少（P值分别为0．014和0．000）。放射治疗前和过程中的电子射野影像系统验证片未发现肿瘤运动到照射野外。结论：靶区中心的平均位置法应用于肺部肿瘤的三维适形放射治疗是可行的。

Validity of mean target center in three dimensional radiotherapy for pulmonary carcinoma

Objective:To study the feasibility of mean target in three dimensional conformal radiotherapy(3D2CRT) for small lesion of lung carcinoma.Methods:Eight patients with 9 small lesions of lung carcinoma treated with 3D-CRT were reviewed.Multiple series phase specific fast CT scans were performed under radiotherapy position and free breathing.Three dimensional reconstructions on each series scans were conducted while the CT scan imaging were transferred to radiotherapy planning system.The tumor center of every series,mean target center,and target volume were then calculated.Beam isocenter was located at the mean target center while optimizing 3D-CRT plan.Verification was performed using electric portal imaging device(EPID)before and during radiotherapy.Target volume of the first series of three dimensional reconstruction added with 10 mm or 20 mm margin was compared with the target volume of mean target center.Results:Compared with the target volumes added with 10 mm or 20 mm,the volume with mean target center was significantly reduced(P=0.014 and 0.000).Conclusions:The mean target center method is feasible for small lesion of lung carcinoma treated with 3D-CRT.