ABSTRACT
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(pitchCON=0.938, pitchS=0.438, and pitchB=1.188)during free breathing. All GTVSwere delineated by the same radiation oncologist using the same contouring protocol. GTVCONgenerated at pitchCON, GTVSgenerated at pitches, and GTVBgenerated at pitchB were compared in terms of volume and geometric position, and GTVSand GTVBwere registered to GTVCONgained at the conventional pitch. The Friedman M and Wilcoxon rank-rum test were used for comparison. Results The volumes of GTVCON, GTVS, and GTVBwere 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 GTVSand GTVCONwas related to the tumor location,so was the MI between GTVBand 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.