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

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

60 mAs to 7.5 mAs Mean ± SD60 Mean ± SD7.5 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
  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 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.