Fig. 1.

Example images of alveolar ventilation (A), perfusion (B), and V̇ _A/Q̇. ratio (C) in a sagittal slice of the right lung in a normal subject (subject 7) in the supine posture. Color scale for ventilation and perfusion in A and B is in units of ml/min/ml of lung. For C it is the dimensionless V̇_A/Q̇ ratio. Dark areas within the images correspond to voxels that do not correlate with the driving function or have a specific ventilation > 1 in image A, to regions of the lung corresponding to large vessels in B, and to both uncorrelated voxels and large vessels in image C.