4DCT容积数据图像重建模式对肺孤立灶内靶区构建的影响

目的 比较4DCT呼吸周期八分法、四分法与传统十分法重建模式对肺孤立灶靶区构建的影响,探讨八分法、四分法在4DCT模拟定位中的可行性。方法 24例肺孤立灶行4DCT扫描,按3种呼吸周期均分法进行图像重建及ITV构建,比较ITV₁₀、ITV₈、ITV₄大小和中心点位置及三维方向运动度。Friedman M法非参数检验差异。结果 ITV₁₀、ITV₈、ITV₄大小分别为(9.09±12.29)、(9.10±12.47)、(8.98±12.61) cm³(P=0.001),ITV₁₀与ITV₈相近(P=0.721),ITV₁₀与ITV₄不同(P=0.002)。ITV₁₀、ITV₈、ITV₄中心点坐标分别为x轴(12.22±7.71)、(12.23±7.71)、(12.22±7.71)(P=0.668);y轴:(43.30±29.38)、(43.30±29.40)、(43.31±29.39)(P=0.643);z轴:(5.66±3.67)、(5.66±3.67)、(5.66±3.67)(P=0.878)。3种重建模式下肿瘤中心在三维方向的运动度分别为x轴:(0.69±0.56)、(0.69±0.68)、(0.79±0.51) mm (P=0.356);y轴:(3.13±3.78)、(3.13±4.05)、(3.19±4.06) mm (P=0.978);z轴:(1.18±1.31)、(1.03±1.32)、(1.16±1.34) mm (P=0.302)。结论 肺孤立灶4DCT模拟定位呼吸周期八分法与十分法重建模式下ITV大小、中心点位置及三维方向的运动度均相近,八分法减少了重建图像的数量和靶区勾画负荷,在4DCT模拟定位中具有可行性。

Comparison of internal tumor volume based on different reconstruction modes of 4DCT for solitary pulmonary lesion

Objective To explore the influence of different reconstruction modes with time-weighted respiratory phases on the internal tumor volume (ITV) of solitary pulmonary lesion (SPL), and to evaluate the feasibilities of 8 and 4 equal time-weighted respiratory phases in 4DCT simulation. Methods 24 patients with SPL underwent 4D scanning. Images were reconstructed with 10, 8 and 4 equal time-weighted phases of the respiratory cycles, respectively. Gross tumor volumes (GTVs) were delineated on the three sets of reconstructed images and fused into ITVs, which were ITV₁₀, ITV₈ and ITV₄ respectively. The differences of volumes, centroid of the ITVs and motions of GTV centroids in three-dimensional directions were compared. Statistical analysis was performed using the Friedman M test. Results The volumes of ITV₁₀, ITV₈ and ITV₄ were (9.09±12.29) cm³,(9.10±12.47) cm³ and (8.98±12.61) cm³(P=0.001), respectively. There were no differences between the volumes of ITV₁₀ and ITV₈ after the Bonferroni correction (P=0.721), while the opposite between those of ITV₁₀ and ITV₄(P=0.002). The differences of centroid positions of ITV₁₀, ITV₈ and ITV₄ in x-, y-and z-axes were all less than 1 mm ((12.22±7.71),(12.23±7.71),(12.22±7.71),P_x=0.668);(43.30±29.38),(43.30±29.40),(43.31±29.39),P_y=0.643;(5.66±3.67),(5.66±3.67),(5.66±3.67),P_z=0.878), similar to the motions of GTV centroids in three reconstructed modes ((0.69±0.56),(0.69±0.68),(0.79±0.51) mm,P_x=0.356;(3.13±3.78),(3.13±4.05),(3.19±4.06) mm,P_y=0.978;(1.18±1.31),(1.03±1.32),(1.16±1.34) mm,P_z=0.302). Conclusions There were no differences in volumes, centroid positions and motions between ITV₁₀ and ITV₈. The quantity of reconstruction images and GTV delineations according to 8 time-weighted phases were both less than conventional 10 phases. 8 time-weighted respiratory phases mode was feasible in 4DCT simulation for SPL.