不同扫描螺距对肺内孤立性病灶GTV构建的影响

目的 比较基于3DCT不同螺距下扫描图像构建的肺内孤立性病灶GTV大小及空间位置差异,探讨大螺距CT扫描在模拟定位中的可行性。方法 选取2014—2015年间肿瘤医院接受放疗的22例周围型肺癌或肺内孤立性转移瘤患者,根据肿瘤所在肺叶不同分为A、B组。在ABC下序贯完成常规螺距(0.938)、小螺距(0.438)及大螺距(1.188)条件下的模拟定位扫描,由同一位医生在相同的窗宽和窗位条件下勾画GTV,比较常规螺距条件下模拟定位所构建的GTVCON、小螺距条件下构建GTVS及大螺距条件下构建GTVB的大小、空间位置及匹配关系。采用Friedman M、Wilcoxon秩和检验。结果 3种螺距下构建的GTVCON、GTVS、GTVB大小分别为(11.58±16.42)、(11.63±17.73)、(12.09±17.46) cm³(P=0.11)。3种螺距下GTV中心点三维坐标比较均相近,A组Px=0.33、Py=0.81、Pz=0.39;B组Px=0.92、Py=0.05、Pz=0.37。GTVS、GTVB相对于GTVCON空间匹配指数与肿瘤所在肺叶的运动幅度有关。结论多层螺旋CT采用不同螺距模拟定位对GTV的大小及空间位置影响不大,适当增加螺距有利于提高扫描速度,缩短模拟定位时间,在肺内孤立性病灶模拟定位中具有可行性。

Effect of CT pitch on the GTV delineation of solitary pulmonary lesion

Objective To explore the effect of pitch in three-dimensional computed tomography (3DCT) on the gross tumor volume (GTV) and spatial position of solitary pulmonary lesion (SPL), and to evaluate the feasibility of high-pitch 3DCT simulation for SPL. Methods Twenty-two patients with peripheral lung cancer or metastatic SPL were divided into groups A and B according to the tumor location. All patients underwent spiral CT scans at different pitches (pitch_CON=0.938, pitch_S=0.438, and pitch_B=1.188) during free breathing. All GTVS were delineated by the same radiation oncologist using the same contouring protocol. GTVCON generated at pitch_CON, GTVS generated at pitches, and GTVB generated at pitchB were compared in terms of volume and geometric position, and GTVS and GTVB were registered to GTVCON gained at the conventional pitch. The Friedman M and Wilcoxon rank-rum test were used for comparison. Results The volumes of GTVCON, GTVS, and GTVB were 11.58±16.42 cm³, 11.63±17.73 cm³, and 12.09±17.46 cm³, respectively (P=0.11). There were no significant differences in the centroid position in x, y, and z directions between GTVCON, GTVS, and GTVB (Px=0.33, Py=0.81, Pz=0.39). The same result was found in group B (Px=0.92, Py=0.05, Pz=0.37). The matching index (MI) between GTVS and GTVCON was related to the tumor location, so was the MI between GTVB and GTVCON. Conclusions The pitch in 3DCT simulation has no significant effect on the GTV and spatial position of SPL. Increasing CT pitch appropriately can improve the scanning speed and shorten the duration of 3DCT simulation, so high-pitch 3DCT simulation is feasible for SPL.