A comparison of the different 3D CT scanning modes on the GTV delineation for the solitary pulmonary lesion

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. GTV(A) and GTV(S) were created from the axial and spiral images, respectively. ITV(MIP) was created from the maximum intensity projection (MIP) reconstructed 4D images. The target volumes and position between GTV(A), GTV(S) and ITV(MIP) were compared. The matching index (MI) between GTV(A) and GTV(S), and the correlation between MI and GTV(S) were evaluated. RESULTS: ITV(MIP) was significantly larger than GTV(A) and GTV(S) (p(s) = 0.000). The ratios of ITV(MIP) to GTV(A) and GTV(S) were 1.57 ± 0.54 and 1.66 ± 0.61, respectively. There was no significant difference between GTV(A) and GTV(S)(p = 0.16). A comparison of the centroidal positions in x, y, and z directions for GTV(A), GTV(S) and GTV(4Dmip) showed no significant difference (p(x) = 0.17, p(y) = 0.40, p(z) = 0.48). Additionally, there was no difference between distances from the centroidal positions of GTV(A) and GTV(S) to the origin of coordinates (p = 0.51). MI between GTV(A) and GTV(S) 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 GTV(A) and GTV(S) was small. A positively correlation was found between MI and GTV(S). Relative to axial scanning mode, spiral CT scan was more timesaving and more efficient, it was feasible in 3DCT simulation for SPL.