Fig. 5.

In a healthy (female, 21 yr old), mild-to-moderate asthmatic (male, 36 yr old), and severe asthmatic (male, 45 yr old) subject, similar delayed wash-in and wash-out phenomena are shown. Color-coded maps indicate initial ventilation classification in the displayed coronal slices. A: regions of interest are circled, highlighting areas of initially poor ventilation (level 1 or 2), which fill to varying degrees following 7.5 s of breath-hold. B: same slices from the same subjects, instead highlighting regions of initial hyperintensity (level 5) that alternatively wash out to varying degrees following breath-hold.