Table 6.

AirT% and AirT* of air-trapped voxels

	Normal Subjects	Severe Asthmatics	P (t-Test)
Total AirT%	3.4 ± 1.2	10.9 ± 1.9	<0.005
AirT*, %
LUL	33.7 ± 2.9	24.8 ± 1.8	<0.05
LLL	9.3 ± 1.6	15.7 ± 1.6	<0.01
RUL	16.2 ± 2.0	19.2 ± 1.6	0.258
RML	30.2 ± 3.8	25.9 ± 2.2	0.349
RLL	10.6 ± 1.6	14.4 ± 1.3	0.075

Values are means ± SE. AirT%, air trapping percentage; AirT*, lobar contribution. A voxel at FRC image is treated as an air-trapped region if its CT intensity of less than −856 Hounsfield units. The difference between AirT% and AirT* is described in Air Trapping.