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Table 1 Comparison between quantitative computed tomography results obtained at 60 and 140 tube current-exposure time producta

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

60 mAs to 140 mAs Mean ± SD60 Mean ± SD140 P r 2 Bias LOA
Baseline ( n = 12) Lung volume (ml) 2,782 ± 666 2,785 ± 671 0.88 0.99 1.7 -114.0 to 109.0
  Lung tissue mass (g) 679 ± 102 683 ± 101 0.12 1.00 -4.5 -13.2 to 4.2
  Hyperinflated tissue (%) 0.6 ± 1.1 0.5 ± 1.0 0.08 0.97 0.1 -0.4 to 0.5
  Normally aerated tissue (%) 86.6 ± 2.9 86.4 ± 3.2 0.52 0.95 0.2 -1.7 to 2.1
  Poorly aerated tissue (%) 11.5 ± 3.4 11.8 ± 3.7 0.21 0.95 -0.3 -2.0 to 1.3
  Nonaerated tissue (%) 1.4 ± 0.5 1.3 ± 0.7 0.07 0.98 0.1 -0.1 to 0.2
ARDS ( n = 28) Lung volume (ml) 2,022 ± 338 2,023 ± 343 0.91 0.99 -0.7 -64.3 to 62.8
  Lung tissue mass (g) 1,500 ± 159 1,498 ± 151 0.73 0.98 1.8 -51.4 to 55.0
  Hyperinflated tissue (%) 0.0 ± 0.1 0.0 ± 0.1 0.52 0.95 0.0 -0.1 to 0.1
  Normally aerated tissue (%) 11.4 ± 11.1 11.4 ± 11.1 0.91 0.99 0.0 -2.4 to 2.4
  Poorly aerated tissue (%) 33.1 ± 15.6 33.2 ± 16.0 0.72 0.98 0.0 -4.5 to 4.4
  Nonaerated tissue (%) 55.4 ± 23.2 55.4 ± 23.5 0.99 0.99 0.0 -5.5 to 5.5
  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 140 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 140 mAs; bias and LOA = bias and limits of agreement (bias ± 1.96 SD) of the Bland-Altman analysis.