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

Abstract

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), Px=0.668); (43.30±29.38), (43.30±29.40), (43.31±29.39), Py=0.643; (5.66±3.67), (5.66±3.67), (5.66±3.67), Pz=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, Px=0.356; (3.13±3.78), (3.13±4.05), (3.19±4.06) mm, Py=0.978; (1.18±1.31), (1.03±1.32), (1.16±1.34) mm, Pz=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. Key words: Tomography, X-ray computed, four-dimensional; Imaging reconstruction; Internal target volume; Lung neoplasms/radiotherapy