图像引导自主呼吸控制下肝脏肿瘤计划靶区外放研究

Design of planning target volume margin using an active breathing control and Varian image-guided radiotherapy（IGRT） system in unresectable liver tumor

目的 图像引导自主呼吸控制（ABC）下肝脏肿瘤适形放疗计划靶体积（刚）外放范围。方法 应用瓦里安公司图像引导放疗（IGRT）系统，对13例经肝动脉栓塞化疗（TACE）的患者，在kV透视测量ABC下碘油影像的稳定性后，以锥形束CT（CBCT）联合ABC技术于每次治疗前采集容积CT图像10次／人。根据碘油影像进行kV-CBCT和计划CT的3D-3D配准，并以此校正摆位误差，设定修正摆位的阈值为3mm。治疗结束后再次采集kV-CBCT和计划CT3D-3D配准验证。结果 ABC kV透视模式下碘油几乎不存在运动。根据stroom公式M=2．0∑＋0．7α和测量结果进行计算，治疗前不加修正和使用ABC技术时肝脏治疗的PTV外放x．y、z轴分别为4．4、5．3、7．8mm。采用以上技术进行在线校正时，PTV外放x,y、z轴分别为2．5、2．6、3．9mm。结论 应用ABC技术的肝脏适形放疗，建议PTV外放x、y、z轴分别为5、6、8mm，应用ABC技术结合图像引导适形放疗系统在线治疗前校正时，PTV外放x,y、z轴分别为3、3、4mm。

Objective To-define the planning target voiume（PTV） margin with an active breathing control （ABC） and the Varian image-guided radiotherapy （IGRT） system. Methods Thirteen patients with liver cancer were treated with radiotherapy from May 2006 to September 2006. Prior to radiotherapy, all patients had undergone transarterial chemoembolization （TACE） by infusing a mixture of iodized oil contrast medium and chemotherapeutic agents, kV fluoroscopy was used to measure the potential motion of lipiedol spot positions during ABC breath-holds. ABC was used for planning CT scan and radiation delivery with the breath held at the same phase of the respiratory cycle （near end-exhalation）. Cone beam CT （CBCT） was taken using Varian IGRT system,which was then compared online with planning CT using a 3D-3D matching tool . Analysis relied on lipiodol spots on planning CT and CBCT mannully. The treatment table was moved to produce acceptable setup before treatement delivery. Repeated CBCT image and another analysis were obtained after irradiation. Results No motion of the intrahepatic tumor was observed on fluoroscopy during ABC breath-holds. The estimated required PTV margins, calculated according to the stroom formula, were 4.4 mm, 5.3 mm and 7.8 mm in the x, y and z axis directions before radiotherapy. The corresponding parameters were 2.5m, 2.6 mm and 3.9 mm after radiotherapy. Conclusions We have adopted a PTV margin of 5 mm,6 mm and 8 nun in the x, y and z axis directions with ABC, and 3,3 and 4 mm with ABC and on-line kilovohage CBCT.