Low-dose CT for quantitative analysis in acute respiratory distress syndrome

Table 3 Comparison between quantitative computed tomography results obtained at 60 and 7.5 tube current-exposure time product^a

60 mAs to 7.5 mAs		Mean ± SD₆₀	Mean ± SD_7.5	P	r ²	Bias	LOA
Baseline ( n = 16)	Lung volume (ml)	3,180 ± 1,096	3,162 ± 1,083	0.18	1.0	17.7	-87.9 to 123.3
	Lung tissue mass (g)	726 ± 106	716 ± 111	0.12	0.96	9.8	-39.2 to 58.8
	Hyperinflated tissue (%)	2.7 ± 4.0	4.2 ± 4.7	<0.001	0.94	-1.5	-4.1 to 1.1
	Normally aerated tissue (%)	81.9 ± 7.1	79.6 ± 5.6	0.002	0.90	2.3	-2.9 to 7.6
	Poorly aerated tissue (%)	13.4 ± 6.9	14.1 ± 6.4	0.50	0.88	-0.7	-5.4 to 3.9
	Nonaerated tissue (%)	2.1 ± 1.4	2.2 ± 1.3	0.09	0.98	-0.1	-0.5 to 0.3
ARDS ( n = 17)	Lung volume (ml)	2,321 ± 499	2,281 ± 478	0.01	0.99	40.4	-73.8 to 154.6
	Lung tissue mass (g)	1,807± 286	1,797 ± 295	0.41	0.97	10.0	-86.1 to 106.1
	Hyperinflated tissue (%)	0.0 ± 0.0	0.1 ±0.0	0.004	0.79	0.0	-0.1 to 0.0
	Normally aerated tissue (%)	9.1 ± 9.5	8.7 ± 9.1	0.20	0.98	0.4	-2.1 to 3.0
	Poorly aerated tissue (%)	27.3 ± 13.7	30.2 ± 11.3	0.008	0.95	-2.9	-10.5 to 4.8
	Nonaerated tissue (%)	63.5 ± 21.4	61.1 ± 18.8	0.03	0.97	2.4	-5.9 to 10.8

^aARDS = acute respiratory distress syndrome; mAs = tube current-exposure time product; lung volume = total lung volume; lung tissue mass = total mass of lung tissue; hyperinflated tissue = mass of hyperinflated tissue; normally aerated tissue = mass of normally aerated tissue; poorly aerated tissue = mass of poorly aerated tissue; nonaerated tissue = mass of nonaerated tissue; P = P-value of the comparison between values obtained at 60 and at 7.5 mAs by paired t-test or signed rank-sum test as appropriate; r² = coefficient of determination of linear regression between values obtained at 60 and 7.5 mAs; bias and LOA = bias and limits of agreement (bias ± 1.96 SD) of the Bland-Altman analysis.

ISSN: 1364-8535