The optimal slice thickness of CT in revealing lobulation of malignant solitary pulmonary nodules

Objective The aim of this study was to determine an optimal slice thickness that was efficient in revealing lobulation of malignant solitary pulmonary nodules (SPNs) on multi-slice spiral computed tomography (MSCT) images preliminarily. Methods Fifty patients with malignant SPNs (diameter ≤ 3 cm) underwent multidetector-row computed tomography of the chest in a single-breath-hold technique. The raw data were acquired with a collimation of 0.625 mm. Three sets of contiguous images were reconstructed with 1-, 2-, and 5-mm slice thickness, respectively. The lobulation sign of SPNs on the computed tomography (CT) images presented in 1-, 2-, and 5-mm slice thickness was compared. Using the 1-mm sections as the gold standard, an optimal slice thickness in revealing lobulation sign of SPNs was determined. Results The 1-mm-thick images CT revealed 98 lobulations (25 with chord distance < 1 mm; 30 with chord distance 1–2 mm; 43 with chord distance > 2 mm) of 45 malignant SPNs. 18 lobulations with chord distance < 1 mm presented in 2-mm-thick sections were as same as those in 1-mm-thick sections. Statistically significant difference in lobulations number was found between that revealed in 2-mm-thick images and that in 1-mm-thick images ( P = 0.023 < 0.05). 16 lobulations with chord distance < 1 mm presented in 5-mm-thick sections were as same as that in 1-mm-thick sections. There was statistically significant difference in lobulations number between that revealed in 5-mm-thick images and that in 1-mm-thick images ( P = 0.004 < 0.05). The 24 lobulations with chord distance 1-2 mm presented in 2-mm-thick sections were as same as that in 1-mm-thick sections. No statistically significant difference in lobulations number were found between that revealed in 2-mm-thick images and that in 1-mm-thick images ( P = 0.261 > 0.05). 13 lobulations with chord distance 1-2 mm presented in 5-mm-thick sections were as same as that in 1- mm-thick sections. There was statistically significant difference in lobulations number between that revealed in 5-mm-thick images and that in 1-mm-thick images ( P = 0.003 < 0.05). 40 lobulations with chord distance s>2 mm presented in 2-mm-thick sections were as same as that in 1-mm-thick sections. No statistically significant difference in lobulations number was found between that revealed in 2-mm-thick images and that in 1-mm-thick images ( P = 0.631 > 0.05). 36 lobulations with chord distance >2 mm presented in 5-mm-thick sections were as same as that in 1-mm-thick sections. There was no statistically significant difference in lobulations number between that revealed in 5-mm-thick images and that in 1-mm-thick images ( P = 0.264 > 0.05). Conclusion It is suggested that the use of 1-mm slice thickness is suitable in revealing lobulations with chord distance < 1 mm. A 2-mm slice thickness is suggested to be used in revealing lobulations with chord distance 1-2 mm and 5-mm slice thickness to be used in revealing lobulations with chord distance > 2 mm.