Ct scanners

We performed 128 slices of chest CT scans with Incisive Philips CT scanners (Amsterdam, The Netherlands). CT examinations were performed with the patient in the supine position in breath-hold, and inspiration using a standard dose protocol, without contrast intravenous injection. The scanning range was from the apex to the base of the lungs. The tube voltage and the current tube were 120 kV and 100–200 mA (and if applicable, using z-axis tube current modulation), respectively. All data were reconstructed with a 0.6–1.0 mm increment. The matrix was 512 mm × 512 mm. Images were reconstructed using a sharp reconstruction kernel for parenchyma evaluation and hard reconstruction kernel for other lung evaluation. All data were reconstructed with a 0.6–1.0 mm increment. Multiplanar reconstruction was also calculated. Details are provided in previous papers [8 (link),11 (link)].

The clinical records of selected cases were screened to ensure that no other clinical indication for the CT scans was present, and the medical history confirmed the absence of underlying pulmonary disease. Patient characteristics, including age, sex, and smoking status, were recorded for each subject. Cases were excluded if their medical history was missing, the quality of the CT scan was suboptimal (e.g., due to technical faults, extensive imaging artifacts, atelectasis, or pleural fluid obscuring more than one pulmonary lobe), or if a new pulmonary diagnosis was detected on the CT scan (e.g., previously unknown diseases such as pneumonia, emphysema, or cancer). Bullae were defined according to radiologic standards as thin-walled (<1 mm) cavities (Hansell et al., 2008 (link)). Blebs were grouped in with the bullae as a subgroup of bullae, as blebs could be classified as bullae with a direct connection to pleura. We classified all bullous air-filled anomalies as bullae either in direct contact with the pleura, or as intrapulmonary bullae. The following CT scanners were used: 2008 GE Discovery, 2015 Philips Brilliance iCT 256 slice detector, 2015 Philips Ingenuity 128 slice detector and the 2017 GE revolution scanner. The majority of scans were made using the Philips CT scanners from 2015.