Fig. 1 The plots of standard deviation of three measurements (logarithmically transformed volumes) for every nodule against their mean in each setting. a 1 mm section thickness and soft kernel, b 2 mm and soft kernel, c 2 mm and sharp kernel. Less variability was found in setting A than in B and C 1183 purely intra-parenchymal nodules with settings A and C, but not with setting B (Table 2). Effect of setting and repeat measures on the measured volume The results of multi-level modelling are shown in Table 3. In this multi-level model, settings A and C both yielded a 1.29 [95% confidence interval (CI): 1.03–1.63] times higher estimate of the volume than setting B (P= 0.03). Measuring time also yielded a significant though very small effect on the measured volume: the second and third measures yielded a 1.01 (95% CI: 1–1.02) times higher estimate for volume than the first measure, which indicated a 1% difference (P= 0.03). It turned out that the differences between settings A and B, and between settings C and B were the same. The same held for the differences between time 2 and time 1, and for time 3 and time 1. Attached and non-smooth-round nodules yielded 1.74 (95% CI: 1.39– 2.18) and 1.83 (95% CI: 1.42–2.37) times higher estimates of the volume than intra-parenchymal and smooth-round nodules (P < 0.01), which indicated significant differences for the measured volumes of those types of nodules. In addition there was a significant interaction between setting and nodule characteristics (location and morphology) indicating that the effect of the reconstruction setting on the measured volumes was different for the different types of nodules (P < 0.05). Discussion This study demonstrated that the repeatability of volume measurement of pulmonary nodules obtained at 1 mm section thickness combined with a soft kernel was almost two times better than that at 2 mm section thickness combined with a soft kernel and almost four times better than that obtained at 2 mm section thickness combined with a sharp kernel. Furthermore, the setting with 1 mm section thickness and a sharp kernel led to larger volumes, and the effect of setting on the measured volume was different for the different types of nodules. The difference in repeatability among the three settings can serve as an indicator for choosing a certain reconstruc- tion setting for low-dose chest CT, especially in lung cancer screening programs in which volumetric growth assess- ment is integrated into the nodule evaluation algorithm. Higher repeatability translates into more accurate growth assessment. Therefore, we recommend a reconstruction setting with 1 mm section thickness and a soft kernel as the standard reconstruction setting for low-dose CT lung cancer screening considering the volume measurement. Furthermore, if the reconstruction settings are different at follow-up, for example 2 mm at baseline and 1 mm at follow up, we should realise that a volume of 25% may not