Sensation 64 ct scanner

All CT scans were performed using a standardized protocol recommended for use with Apollo analysis software (Vida Diagnostics, Iowa, USA). Multi-Slice Computed Tomography (MSCT) scans were performed on a Siemens Sensation 64 CT scanner (Siemens Medical Solutions, Erlangen, Germany) using a high-resolution algorithm, with detector thickness 0.75 mm, pitch 1.0, effective mAs 90 and a tube voltage of 120 kV. The high-resolution algorithm was chosen to ensure the best visualization of the airway tree^{37 (link)}. The scanning protocol was performed at maximal inspiration and expiration, with breath hold, for the duration of the scan (approximately 10–15 sec depending on the size of the thorax). All patients are coached beforehand and during the scan in a standardized manner, conforming with the Vida Diagnostics protocol and as used by other centers^{38 (link),39 (link)}. The images were reconstructed using a slice thickness of 0.75 mm, a reconstruction increment of 0.5 mm, and a sharp reconstruction algorithm. Additional reconstructions were also performed using several soft reconstruction kernels, including B30f and B35f, which were chosen to suit the recommended protocol in the Apollo analysis software.

All patients underwent multidetector CT (Siemens Sensation 64 CT scanner [32 detector], Siemens Medical Solutions, Malvern, PA) at baseline, and consecutively after 3, 12 and 24 months, comprising a total of 64 exams, i.e. 128 volumetric datasets. Exclusively non-enhanced spirometer-controlled paired inspiratory (100kVp, 30–50mAs; Pitch 1.0) and expiratory (100kVp, 30–50mAs; Pitch 1.2) CT was routinely performed in supine position as reported previously [15 (link), 29 (link), 30 (link)]. Specifically, spirometer control was employed to achieve full inspiration, and maximum expiration to near residual volume. The total estimated effective dose for the 4 serial CT scans over the 2 year period was 5.4–5.6 mSv. Reconstruction was performed in a medium soft B30f, as recommended for parenchyma quantification, as well as a sharp B60f algorithm [16 (link), 20 (link), 30 (link)]. All examinations were visually inspected by a reader with more than 20 years (BN) of experience in pediatric chest imaging for adequate inspiration, absence of significant motion artifacts and inclusion of all parts of the chest. The examination protocol and equipment were kept exactly constant during the study period.