Table 3.

Extrapolation method in humans

CT Variables	Spiral	Extrapolation 20 mm	ρ	Bias (LOA)
Total lung volume (ml)	3700 (2908–5327)	3736 (2896–5313)	0.997	6 (−60 to 72)
Total lung weight (g)	912 (754–1147)	903 (771–1155)	0.997	2 (−37 to 41)
Hyper-aerated tissue (%)	2.5 (0.1–9.1)	2.3 (0.1–9.1)	0.999	0.1 (−0.4 to 0.5)
Normally aerated tissue (%)	65.5 (50.1–77.1)	66.4 (49.5–77.2)	0.996	0.0 (−1.9 to 1.9)
Poorly aerated tissue (%)	15.0 (11.3–18.7)	15.4 (11.3–18.7)	0.982	0.1 (−1.1 to 1.4)
Non-aerated tissue (%)	8.0 (3.1–27.5)	7.1 (3.1–26.4)	0.986	−0.2 (−2.2 to 1.8)

Comparison between CT analysis performed on the reference spiral scan and extrapolated from a subset of slices interleaved by 20 mm (Extrapolation 20 mm). ρ is Spearman’s rank correlation between extrapolated variables and the reference ones. Data are medians (interquartile ranges). Bias (LOA) is the result of the Bland–Altman analysis, reported as bias (limits of agreement)