Photon-Counting CT for COPD

Purpose and objective: This project aims to evaluate photon-counting computed tomography (PCCT) quantitative accuracy using COPDGene subjects. The goal is to establish acquisition protocols for PCCT scans with proper post-processing (e.g., reconstruction parameters and harmonization techniques) that enable reproducible measurements of emphysema metrics (e.g., Perc15, LAA-950, HU accuracy) and airways (Pi10, WA%) in the lungs. Study activities and population group: The study will recruit subjects from a current study at Duke (COPDGene Phase 4, Pro00113442). Here are the aims: * The research team will request consent from participants to acquire PCCT scans at their Phase 4 COPDGene visit. Scans will be performed using a PCCT-specific protocol. * Reconstruct the PCCT images with multiple post-acquisition parameter settings. Apply harmonization techniques that are recently developed by the investigators of this study. Data analysis: * Identify the reconstruction and harmonization conditions that enable reproducible measurements of emphysema metrics (perc15, LAA-950, HU accuracy) and airways (Pi10, WA%), when compared to the counterpart EICT scans. * Demonstrate the non-inferiority and potentially improved capabilities of PCCT scans in cross-sectional and longitudinal studies. Risk/safety issues: The participants are asked to get an additional CT scan with a PCCT scanner at their COPDGene Phase 4 visit. This additional CT scan will be done using an inspiratory chest protocol with a total of 3 mGy (\~1.5 mSv) radiation dose. This is roughly equivalent of 6 month of background radiation. Women who are pregnant will not have a chest CT scan done until they are confirmed to be not pregnant.