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Table 2 Comparison between quantitative computed tomography results obtained at 60 and 15 tube current-exposure time producta

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

60 mAs to 15 mAs

Mean ± SD60

Mean ± SD15

P

r 2

Bias

LOA

Baseline ( n = 18)

Lung volume (ml)

3,227 ± 1,015

3,224 ± 995

0.80

1.0

3.4

-112.0 to 118.8

 

Lung tissue mass (g)

711 ± 128

707 ± 129

0.17

0.99

4.3

-21.8 to 30.4

 

Hyperinflated tissue (%)

3.3 ± 5.5

3.9 ± 5.6

<0.001

0.99

-0.7

-1.8 to 0.5

 

Normally aerated tissue (%)

81.4 ± 7.5

81.1 ± 6.6

0.22

0.93

0.3

-4.2 to 4.8

 

Poorly aerated tissue (%)

13.3 ± 6.2

12.9 ± 6.2

0.84

0.91

0.4

-3.3 to 4.1

 

Non aerated tissue (%)

2.1 ± 1.4

2.1 ± 1.5

0.04

0.96

-0.1

-0.6 to 0.5

ARDS ( n = 18)

Lung volume (ml)

2,295 ± 561

2,264 ± 526

0.07

0.99

31.4

-105.8 to 168.6

 

Lung tissue mass (g)

1,778 ± 315

1,775 ± 301

0.78

0.98

3.0

-85.1 to 91.1

 

Hyperinflated tissue (%)

0.1 ± 0.2

0.2 ± 0.2

0.008

0.94

0.0

-0.1 to 0.1

 

Normally aerated tissue (%)

9.3 ± 9.7

8.8 ± 9.4

0.13

0.98

0.5

-2.1 to 3.2

 

Poorly aerated tissue (%)

28.1 ± 13.4

28.6 ± 12.6

0.44

0.96

-0.5

-4.8 to 3.9

 

Non aerated tissue (%)

62.5 ± 21.2

62.5 ± 20.0

0.98

0.98

0.0

-6.9 to 6.9

  1. 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 15 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 15 mAs; bias and LOA = bias and limits of agreement (bias ± 1.96 SD) of the Bland-Altman analysis.