CT scan protocols
CT scans obtained within 30 days of the treatment start date were analyzed. If there was more than one CT scan, the closest CT scan before the biopsy was used. The included patients underwent CT scans with the following four scanners: Somatom Definition Flash, Siemens, Germany; uCT780, United Imaging, Shanghai, China; Somatom Perspective 128, Siemens, Germany; and Somatom Definition Force, Siemens, Germany. Scanning protocols were as follows: 120 kVp, 100–200 mAs, and pitch 0.75–1.5. Plain CT images with 5-mm thickness cuts were retrieved from the Picture Archiving and Communication System (PACS) for further analysis. CT images were acquired in the supine position at full inspiration for all patients.