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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.