Abstract
OBJECTIVES: To investigate the impacts of the different three-dimensional CT (3DCT) scanning modes on the GTV delineation for solitary pulmonary lesion (SPL) based on four-dimensional CT (4DCT), and to evaluate the feasibility of using the spiral CT scan in CT simulation. MATERIALS AND METHODS: Twenty-one patients with SPL underwent axial CT scan, spiral CT scan and 4DCT simulation scan during free-breathing, respectively. The same clinical radiation oncologist delineated the gross tumor volume (GTV) under the same CT window setting. GTVA and GTVS were created from the axial and spiral images, respectively. ITVMIP was created from the maximum intensity projection (MIP) reconstructed 4D images. The target volumes and position between GTVA, GTVS and ITVMIP were compared. The matching index (MI) between GTVA and GTVS, and the correlation between MI and GTVS were evaluated. RESULTS: ITVMIP was significantly larger than GTVA and GTVS (ps = 0.000). The ratios of ITVMIP to GTVA and GTVS were 1.57 ± 0.54 and 1.66 ± 0.61, respectively. There was no significant difference between GTVA and GTVS(p = 0.16). A comparison of the centroidal positions in x, y, and z directions for GTVA, GTVS and GTV4Dmip showed no significant difference (px = 0.17, py = 0.40, pz = 0.48). Additionally, there was no difference between distances from the centroidal positions of GTVA and GTVS to the origin of coordinates (p = 0.51). MI between GTVA and GTVS was 0.41 ± 0.24 (range 0-0.89), and it was positively correlated with the tumor volume (r = 0.64, p = 0.002). CONCLUSION: There was no impact on the volume or centroidal position of GTV by the axial scan or spiral scan in 3DCT simulation for SPL. MI between GTVA and GTVS was small. A positively correlation was found between MI and GTVS. Relative to axial scanning mode, spiral CT scan was more timesaving and more efficient, it was feasible in 3DCT simulation for SPL.