肺癌三维适形放射治疗靶体积确定的影响因素

目的 尽可能合理地确定肺癌三维适形放射治疗的计划靶体积。方法 用透视法观察59例不同解剖部位肺部原发病灶(非小细胞肺癌)随生理活动的移动幅度；用射野片(portal film)测量肺癌放射治疗过程中射野不同方向的移动幅度，计算其随机误差、系统误差和总误差；由5位放射治疗科医生单独在治疗计划CT上勾画大体肿瘤体积(GTV)，比较其中心层面与原计划勾画的吻合性，比较辐射线状测量差异(RLMV)值。结果 以肺下野肿块在头脚方向的移动幅度最大，为14．3mm;肺中野肿块为7．1mm；而左右方向和前后方向的移动范围在4．0mm之内。肺癌放射治疗过程中的移动误差在左右方向为4．2mm，头脚方向为4．6mm；随机误差为3．4mm，系统误差为6．0mm，总误差为6．9mm。与原治疗计划GIV相比，单个放射治疗医生勾画GTV的体积最大相差1．5倍，GTV中心层面与原计划的中心层面无一例完全吻合；RLMV值以向着肺门淋巴结方向的值最大。结论 确定肺癌三维适形放射治疗计划的GTV边界值时应该采取个体化原则，计划靶体积(PTV)应该由一组放射治疗医生共同确定。目前常用的真空体模固定法的误差仍较大，需要进一步改进。

Factors influencing target confirmation in three dimensional conformal radiotherapy for lung cancer

Objective To reasonably confirm the target of 3-dimensional conformal radiation therapy (3DCRT) for lung cancer. Methods While a patient was breathing, the motion of the primary lesion in the lung was observed by fluoroscopy. The extent of motion of the primary lesion during irradiation was evaluated by portal films. Three 3DCRT plannings for lung cancer, in which gross tumor volume (GTV) decided by a group of radiation oncologists and implemented, were taken as the standard. The GTV delineated by five radiation oncologits was compared with the standard by computing the radial line measurement variation (RLMV). Results From fluoroscopic observation in fifty-nine patients, the extent of lesion motion was the largest in cephalo-caudal direction, with 14.3 mm for lesions in the lower and 7.1 mm (median) for middle part of the lung. In lateral and antero-posterior directions, it was within 4. 0 mm. The motion error during irradiation was 4. 2 mm in lateral direction and 4.6 mm in cephalo-caudal direction. The random error, system error and total error for set-up uncertainty were 3.4 mm, 6.0 mm, and 6.9 mm. Compared to the standard, the discrepancy of GTV could be as large as 150% . The largest RLMV was observed in the area of lung hilar nodes. Conclusions The target of 3-dimensional conformal radiation therapy for lung cancer should be confirmed individually and delineated by a group of radiation oncologists. A more efficient fixing device is needed owing to the large total error for set-up.