胸中段食道癌调强放射治疗真空垫与体膜加真空垫的摆位误差比较

Comparison of Setup Errors for Fixed Technology Between Vacuum Pad With Membrane Plus Vacuum Pad in Thoracic Esophageal Carcinoma

目的应用千伏级锥形束CT(KV-CBCT)比较胸中段食道癌患者使用真空垫与体膜加真空垫两种固定技术的摆位误差。方法选取40例患者随机分为两组,各20例。一组使用真空垫固定技术,另一组使用体膜加真空垫固定技术。应用KV-CBCT于放疗实施前对40例胸中段食道癌患者进行扫描,并在线将重建的三维图像与计划CT扫描图像匹配,获得左右(X)腹背(Y)头脚(Z)三个方向摆位误差并进行分析。结果根据Van Herk公式(PTV=2.5∑+0.7δ)计算得到各方向的CTV-PTV外放边界值,热塑体膜加真空垫固定组左右(X)、腹背(Y)、头脚(Z)分别1.60 mm、1.27 mm、1.74 mm,真空垫固定组左右(X)、腹背(Y)、头脚(Z)分别2.47 mm、4.07mm、3.67 mm。结论胸部肿瘤患者由于呼吸动度、胸廓变化、手臂上举牵拉等因素造成摆位误差,使用体膜加真空垫固定技术可减少摆位误差,从而提高摆位治疗精度。

Objective To evaluate setup errors using kilovoltage cone beam computed tomograph （ KV-CBCT ） for thoracic esophageal carcinoma patients treated by the ifxed technology of using vacuum pad and membrane plus vacuum pad.Methods Retrospective study has been carried out for 40 patients, which were separated into two groups. A group of 20 patients were ifxed with vacuum pad; another group of 20 patients were ifxed with the membrane plus vacuum pad. Before radiotherapy, 40 patients of thoracic esophageal carcinoma were scanned by KV-CBCT, and the reconstructed 3 D images and plan CT scan image were matched online, and then get and analyze the setup errors of three directions of left-right （ X ）, ventral-dorsal （ Y ）, cranial-caudal （ Z ）.Results The margins required for CTV-PTV were calculated according to the Van Herk formula （ PTV=2.5 ∑＋0.7 δ）, The thermoplastic membrane plus vacuum pad ifxed groups of left-right （ X ）, ventral-dorsal （ Y ）, cranial-caudal （ Z ） respectively 1.60 mm, 1.27 mm, 1.74 mm; Fixed vacuum pad group of left-right （ X ）, ventral-dorsal （ Y ）, cranial-caudal （ Z ） were 2.47 mm, 4.07 mm, 3.67 mm.Conclusions The thoracic esophageal carcinoma patients due to respiratory movements, thoracic changes, and arm lift factors caused setup errors, using membrane plus fixed vacuum pad technology can reduce the setup errors, so as to improve the setup accuracy of therapy.