OBJECTIVE: To evaluate the influence of nodule margin on inter- and intra-reader variability in manual diameter measurements and semi-automatic volume measurements of solid nodules detected in low-dose CT lung cancer screening.
METHODS: Twenty-five nodules of each morphological category (smooth, lobulated, spiculated and irregular) were randomly selected from 93 participants of the Dutch-Belgian randomized lung cancer screening trial (NELSON). Semi-automatic volume measurements were performed using Syngo LungCARE® software. Three radiologists independently measured mean diameters manually. Impact of nodule margin on inter-reader variability was evaluated based on systematic error and 95% limits of agreement. Inter-reader variability was compared to the nodule growth cutoff as used in Lung-RADS (+1.5mm diameter) and NELSON/British Thoracic Society (+25% volume).
RESULTS: For manual diameter measurements, a significant systematic error (up to 1.2mm) between readers was found in all morphological categories. For semi-automatic volume measurements, no statistically significant systematic error was found. The inter-reader variability in mean diameter measurements exceeded the 1.5mm cut-off for nodule growth for all morphological categories (smooth: ±1.9mm [+27%], lobulated: ±2.0mm [+33%], spiculated: ±3.5mm [+133%], irregular: ±4.5mm [+200%]). The 25%-volume growth cut-off was exceeded slightly for spiculated (28% [+12%]) and irregular (27% [+8%]) nodules.
CONCLUSION: Lung nodule sizing based on manual diameter measurement is affected by nodule margin. Inter-reader variability increases especially for nodules with spiculated and irregular margins, and may cause misclassification of nodule growth. This effect is much smaller for semi-automated volume measurements. Advances in knowledge: Semi-automatic volume measurements are superior for both size and growth determination of pulmonary nodules.
- Journal Article