PET-CT在局部晚期非小细胞肺癌调强放疗靶区勾画中的应用及其影响

目的 探讨局部晚期非小细胞肺癌（NSCLC）调强适形放疗（IMRT）中应用PET-CT融合图像勾画靶区对靶体积及正常肺组织受照剂量的影响。方法 随机选择30例临床分期为ⅢA、ⅢB期的初治NSCLC患者，分别依据单纯增强CT图像和同一固定体位下PET-CT与CT融合后的图像勾画靶区和危及器官。分别比较两种影像资料下所勾画的肿瘤靶区（GTV）、临床靶区（PTV）体积；在PTV的处方剂量达60 Gy/30次时，比较两组放疗计划中双肺的肺受照5 Gy以上剂量的肺体积（V5）、肺受照20 Gy以上剂量的肺体积（V20）及肺受照射的平均剂量（MLD）。结果 30例患者在PET-CT融合组中勾画的GTV体积为（248.39±94.80）cm3，低于单纯CT组的（311.22±99.16）cm3，差异有统计学意义（P＜0.05）。在GTV的基础上外扩得到PTV，30例患者在PET-CT融合组中的PTV体积为（356.68±92.73）cm3，低于单纯CT组的（433.58±107.89）cm3，差异有统计学意义（P＜0.01）。PTV处方剂量达到60 Gy/30次时，30例患者在PET-CT融合组中双肺V5、V20、MLD分别为（51.26±10.50）％、（25.71±5.17）％、（1595.27±148.24）cGy，均低于单纯CT组的（56.41±9.55）％、（29.09±4.10）％、（1693.59±100.60）cGy，差异均有统计学意义（P＜0.05）。结论 应用PET-CT融合图像勾画靶区能提高靶区勾画的精确性，改善靶体积并降低正常肺组织的照射剂量。

PET-CT application and influence on IMRT target delineation in locally advanced non-small cell lung cancer

Objective To investigate the value of PET-CT image fusion to delineate the target of intensity modulated radiation therapy（IMRT） in locally advanced non-small cell lung cancer（NSCLC）， and the impact on target volume and dose of normal lung tissue. Methods Thirty NSCLC patients of clinical stage ⅢA and ⅢB were randomly selected. Target and organ at risk were delineated on the same fixed position according to enhanced CT images and fusion images of PET/CT and CT, respectively. Then the volume of gross tumor volume（GTV） and planning target volume（PTV） under these two status were compared. Moreover， the percent of the total lung volume exceeding 5 Gy（V5）， percent of the total lung volume exceeding 20 Gy（V20）， mean dose of lung irradiated（MLD） in two different conformal IMRT plans were observed when the dosage of PTV was up to 60 Gy/30 f. Results The GTV volume on fusion images of PET-CT/CT was （248.39±94.80）cm3, less than （311.22±99.16）cm3 on the enhanced CT images in 30 cases. The difference was statistically significant（P＜0.05）. PTV， extended from GTV， in fusion images of PET-CT/CT was （356.68±92.73）cm3, while in the enhanced CT images were （433.58±107.89 cm3） with significant difference（P＜0.01）. The V5， V20 and MLD of whole lung in the two plans were compared. In fusion images of PET-CT/CT program， V5， V20 and MLD was （51.26±10.50）％，（25.71±5.17）％ and （1595.27±148.24） cGy, remarkly less than （56.41±9.55）%, （29.09±4.10）% and （1693.59±100.60） cGy in the enhanced CT program with significant difference（P＜0.05）. Conclusion Application of PET-CT/CT fusion image to delineate the targets of IMRT can improve the accuracy of target delineation volume and reduce the dose of normal lung tissues.