Normal spectrum of pulmonary parametric response map to differentiate lung collapsibility: distribution of densitometric classifications in healthy adult volunteers.

• Co-registration of inspiratory and expiratory computed tomography allows dual-phase densitometry. • Dual-phase co-registered densitometry reflects heterogeneous regional changes in lung function. • Quantification of lung in healthy subjects is needed to set reference values. • Expiratory low attenuation areas <30 % could be considered within normal range.