Influence of CT Reconstruction Settings on Extremely Low Attenuation Values for Specific Gas Volume Calculation in Severe Emphysema

The disproportionate effect of low-attenuation pixels on SVg likely causes overestimation of the severity of emphysema and trapped gas. This can be significantly reduced, however, by using thick slices and a smooth filter for image reconstruction. ΔSVg is generally robust for quantifying the functional impairment of the lung in severe emphysema.