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Table 4 Mean differences in MD measures between processed images and the corresponding raw digital image, by reader and mammography system

From: Mammographic density assessed on paired raw and processed digital images and on paired screen-film and digital images across three mammography systems

Reader system Number of images Number of women Percent density Dense area Breast area
     Differencea √PMD (95% CI) Differencea √Dense area (cm) (95% CI) Differencea √Breast area (cm) (95% CI)
Reader 1
  Hologic 234 104 0.91 (0.74, 1.08) 1.17 (0.96, 1.39) 0.01 (−0.03, 0.05)
  GE 232 98 0.62 (0.44, 0.80) 0.79 (0.57, 1.00) 0.09 (0.07, 0.11)
  Fuji 60 15 0.40 (0.20, 0.61) 0.51 (0.26, 0.75) −0.12 (−0.17, −0.08)
  All 526 217 0.72 (0.61, 0.84) 0.93 (0.79, 1.06) 0.03 (−0.08, 0.84)
  p for heterogeneityb     0.007   0.003   <0.001
Reader 2
  Hologic 246 109 −0.47 (−0.64, −0.30) −0.60 (−0.85, −0.34) 0.05 (0.01, 0.09)
  GE 218 95 0.05 (−0.12, 0.23) 0.07 (−0.15, 0.30) 0.11 (0.07, 0.16)
  Fuji 60 15 −0.76 (−1.03, −0.48) −0.92 (−1.27, −0.57) 0.06 (−0.01, 0.12)
  All 524 219 −0.28 (−0.40, −0.17) −0.36 (−0.52, −0.19) 0.08 (0.05, 0.11)
  p for heterogeneityb     <0.001   <0.001   0.09
Reader 3
  Hologic 232 98 0.10 (−0.04, 0.24) 0.12 (−0.07, 0.31) 0.01 (−0.03, 0.04)
  GE 222 95 0.69 (0.52, 0.85) 0.88 (0.64, 1.12) 0.00 (−0.03, 0.04)
  Fuji 460 200 0.10 (−0.02, 0.23) 0.13 (−0.03, 0.29) 0.03 (−0.01, 0.08)
  All 914 392 0.24 (0.16, 0.33) 0.31 (0.20, 0.43) 0.02 (0.00, 0.04)
  p for heterogeneityb     <0.001   <0.001   0.48
Reader 4
  Hologic 834 417 0.55 (0.44, 0.65) 0.74 (0.60, 0.89) −0.09 (−0.10, −0.08)
  GE 360 180 0.43 (0.28, 0.58) 0.50 (0.34, 0.67) 0.08 (0.01, 0.16)
  All 1194 597 0.51 (0.43, 0.60) 0.67 (0.56, 0.78) −0.04 (−0.07, −0.02)
  p for heterogeneityb     0.21   0.056   <0.001
All readers combined
  Hologic 1546 679 0.37 (0.29, 0.45) 0.50 (0.39, 0.61) −0.04 (−0.05, −0.03)
  GE 1032 418 0.45 (0.34, 0.56) 0.56 (0.42, 0.69) 0.07 (0.04, 0.10)
  Fuji 580 200 0.04 (−0.09, 0.18) 0.06 (−0.10, 0.23) 0.02 (−0.03, 0.07)
  All 3158 1297 0.34 (0.28, 0.40) 0.44 (0.36, 0.52) 0.01 (−0.01, 0.02)
  p for heterogeneityb     <0.001   <0.001   <0.001
  1. p for heterogeneity <0.001 between readers for each of the Hologic, GE and Fuji systems, for both percent density and dense area. For breast area, p for heterogeneity <0.001 also between readers on the Hologic system, and no difference between readers for breast area was found for GE (p = 0.07) and Fuji (p = 0.08)
  2. aDifferences are processed–raw images
  3. b p value for heterogeneity between systems, for a given reader
  4. CI confidence interval, MD Mammographic density, GE General Electric, PMD percent mammographic density