Table 2.

Functional and structural lung parameters derived from micro-CT scans^a

	Name	Description	Unit	Formula
Micro-CT readouts (p = P01 or P02)	N p	Number of Voxel that compose segmentation	/	Number of voxels
	V p	Total Lung Volume	mm3	Np × Voxel size
	MLAp	Mean Lung attenuation	HU	$\sum _{i=1}^{N_p}{\text{HU}}_i/N_p$
	Gasp	Content of gas inside the lung	mm3	$\frac{V_p\times {\text{MLA}}_p}{-1,000}$
Aeration compartments	%Normo	% Normo-aerated volume: % of lung with high content of gas	%	Percentage of voxel in HU range [−860; −435]
	%Hypo	% Hypo-aerated volume: % of lung with low content of gas	%	Percentage of voxel in HU range (−435; −121)
	%Non	% Non-aerated volume: % of lung with no gas	%	Percentage of voxel in HU range [−121; 121]
Micro-CT biomarkers of interest	Tissue	Volume of parenchyma without Gas component (calculated in P02)	mm3	VP02 – GasP02
	%GasP01	Percentage of gas inside the lung in P01	%	GasP01 × 100/VP01
	%GasP02	Percentage of gas inside the lung in P02	%	GasP02 × 100/VP02

HU, Hounsfield units; micro-CT, micro-computed tomography. ^aParameters derived from micro-CT scans were divided into three main groups: 1) micro-CT readouts of volumes and densities; 2) aeration compartments, “normal,” “low,” and “no” gas, with the latter two considered as densitometric biomarkers of fibrosis; 3) lung “tissue” and “gas” (%Gas_P01 and %Gas_P02) as structural biomarkers of inflammation and fibrosis.