目的：研究非小细胞肺癌（NSCLC）放疗过程中再次CT 定位及相应放疗计划修改对肿瘤区及正常组织剂量学影响。方法对53例经病理证实的NSCLC患者放疗过程中进行再次定位，根据肿瘤及肺体积变化，修改放疗计划，通过拟合两次计划，分析叠加的剂量体积参数，与不修改的放疗计划的剂量体积参数比较。结果放疗计划修改前照射次数为（20.0±4.2）次，计划修改后G T V缩小了（71.98±34.6） cm3，且 G T V 变化与计划修改前照射次数呈正相关关系，r＝0.497，P＝0.006。最初设计的总计划与再次C T设计的计划拟合后患侧肺和全肺的平均受量分别下降了（4.6±10.1）％、（4.1±8.7）％，P值分别为0.03和0.02。拟合叠加计划与初次总的计划比较，心脏的V30受照射剂量下降了（2.68±1.3）％，脊髓的Dmax下降了（12.4±2.8）％。结论三维适形放疗中肿瘤体积发生退缩，可以适时地修改放疗计划以减少正常组织的受照射剂量，从而可以推量照射以提高肿瘤的受照射剂量。%Objective To study the change of target volume during radiotherapy for non‐small cell lung cancer (NSCLC) and the inference of treatment plan changing for normal tissue .Methods Fifty‐three NSCLC patients were treated with 3D‐CRT scanned by CT repeatedly and treatment plan changed according to the tumor and lung volume change .Results Totally patients with (20.0+ 4.2) irradiation fractions before treatment plan changing .The GTV shrinkaged (71.98 ± 34.6) and the change of GTV was positively correlated with irradiation fractions before radiotherapy plan changing(r=0.497 ,P=0.006) .Mean lung dose of ipsilateral and all lung descended (4.6 ± 10.1) and (4.1 ± 8.7) ,compared with the first plan .V30 irradiated dose dropped (2.68+1.3)% and the Dmax of spinal cord descended (12.4 +2.8)% .Conclusion Primary tumor volume changed constantly during 3D‐CRT ,we can duly modify radiotherapy plan to reduce the exposure dose of normal tissue ,which could im‐prove the irra diated dose of the tumor .
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