基于PET-CT与4DCT的NSCLC的PTV比较

目的 比较NSCLC基于FDG PET-CT与4DCT定义的原发肿瘤PTV间位置及体积差异。方法 15例NSCLC患者序贯完成胸部3DCT、4DCT及FDG PET-CT扫描。在4DCT 10个呼吸时相图像上勾画原发肿瘤GTV并融合获得IGTV₁₀。基于PET图像原发肿瘤SUV_max的15%勾画靶区定义为IGTV_PET。分别基于IGTV₁₀、IGTV_PET外扩10 mm得到PTV_4D和PTV_PET。比较PTV_PET与PTV_4D间位置、体积及DI值差异。结果 PTV_PET和PTV_4D中心点位置差异无统计学意义(P=0.589、0.147、0.096)。PTV_PET和PTV_4D体积差异无统计学意义(P=0.156),但5例PTV_PET相对于PTV_4D变化率>20%,10例PTV_PET>PTV_4D,平均增加30%,5例PTV_PET4D,平均减少11%。PTV_4D对PTV_PET的DI平均值为85%,有7%~46%的PTV_PET未能被PTV_4D所覆盖;PTV_PET和PTV_4D间的DI同三维运动矢量无相关性(P=0.134、0.405)。结论 尽管基于FDG PET-CT与基于4DCT所构建NSCLC原发肿瘤PTV中心点位置及体积差异并不显著,但相互DI值所反映的两靶区空间错位明显且这种错位与肿瘤位移大小并无相关性。

Comparison of PTV based on FDG PET-CT versus 4DCT in non-small cell lung cancer

Objective To compare the positional and volumetric differences of planning target volumes (PTVs) based on fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET-CT) and four-dimensional CT (4DCT) for the primary tumor of non-small cell lung cancer (NSCLC). Methods Fifteen patients with NSCLC sequentially underwent three-dimensional CT(3DCT), 4DCT, and FDG PET-CT scans of the thorax. IGTV₁₀ was defined on 10 respiratory phases of 4DCT images;IGTV_PET was defined on PET-CT images using a fixed threshold of 15% of the maximum standard uptake values. PTV_4D and PTV_PET were obtained by adding a 10 mm margin around IGTV₁₀ and IGTV_PET. The differences in volume, position, and degree of inclusion (DI) between PTV_PET and PTV_4D were evaluated. Results There was no significant difference in centroid position between PTV_PET and PTV_4D (P=0.589, 0.147, and 0.096). There was no significant difference in volume between PTV_PET and PTV_4D (P=0.156);however, PET-CT resulted in an>20% change in PTV in 5 of 15 patients, the PTV_PET volume increased (average 30%) in 10 patients, and the PTV_PET volume decreased (average 11%) in 5 patients. The mean DI of PTV_4D in PTV_PET was 85%, and 7%-46% of PTV_PET was not included within the PTV_4D. The DI between PTV_4D and PTV_PET showed no significant correlation with the 3D motion vector (P=0.134 and 0.405). Conclusions Although there are no significant differences in centroid position and volume between PTV_PET and PTV_4D for the primary tumor of NSCLC, the spatial mismatch between them is apparent and the mismatch shows no correlation with tumor displacement.