Fig. 1. Illustration and CT images of CTP674 lung phantom (The Phantom Laboratory).

A. Illustration of CTP674 lung phantom. Nine air columns with three different diameters and volumes were chosen for EV measurements (E1–E9), and three polycarbonate tubes (airway tubes) with different wall thicknesses and angles were analyzed for airway wall measurements (A1–A3). Two airway tubes (A1 and A2) were placed at different angle of 30° from z-axis of CT couch. B. CT scans with various algorithms at low-dose setting. C. CT scans with various algorithms at standard-dose setting. CT = computed tomography, EV = emphysema volume, FBP = filtered back projection, IMR-R1 = MIR with image definition of body routine level 1, IMR-SP1 = MIR with image definition of sharp plus level, IMR-ST1 = MIR with image definition of body soft tissue level 1, MIR = model-based iterative reconstruction, VME70 = standard virtual monoenergetic dataset at 70 keV