Pulmonary nodules: Assessing the imaging biomarkers of malignancy in a "coffee-break"

Purpose To prospectively assess the repeatability of CT texture features and semi-automated volume measurements extracted from pulmonary nodules (PNs) at low-dose multi–detector row computed tomography (CT). The secondary objective was to investigate the influence of two methods of inspiratory control on the repeatability of CTTA and volumetry. Introduction Although nodule volumetry is a recognized biomarker of malignancy in pulmonary nodules (PNs), caution is needed in its interpretation because of variables such as cardiac motion, respiratory volume variation and inter-scan variability of up to 25%. The alternative technique of CT texture as a potential independent biomarker of malignancy has been suggested, but interscan variability and respiratory volume variation has not been assessed. Materials and methods 40 patients (20 with an indeterminate PN and 20 with pulmonary metastases) underwent two Low Dose CT scans (LDCT) within a 60-minute period (the “Coffee-break”). Patients were randomized to two inspiratory control groups: normal breath hold, and controlled lung volume. 20 texture features were extracted from each automatic contoured region surrounding the PN. The variability and limits of repeatability of texture measurements within individual nodules was assessed. Results The mean difference in volume between the two scans was 6.3%, SD: 29.9%. The 20 textural features displayed 95% CI below ±17.8%, and were less variable than nodule volume (95% CI ±28.9%). All features had high repeatability, calculated by the concordance correlation coefficient, (0.84 ≤ CCC ≤ 0.99). All measurements were more repeatable for the controlled lung volume group than the normal breath-hold group. Conclusion CTTA repeatability was comparable to automatic volumetric measurements, and appears to be improved using controlled volume breath holding.