Table 1.

Mammographic features as assessed by the threshold and SMF methods: percentiles and agreement between breasts and by view

Breast size
Dense tissue
Nondense tissue
Percent density including edge
Percent density excluding edge
Threshold measure (units):
Area (cm2)
Area (cm2)
Area (cm2)
Of projected area (%)
NA
SMF measure (units):Volume (cm3)Volume (cm3)Volume (cm3)Of breast volume (%)Of breast volume excluding edge (%)
CC views (244 women, 485 films)
ThresholdPercentiles: 50th (25, 75)
Left171 (126, 225)20.8 (9.5, 33.0)146 (99, 207)12.8 (4.8, 23.6)
Right164 (118, 221)19.6 (8.9, 34.6)143 (98, 197)13.5 (4.6, 23.6)
Test for left-right differenceP = 0.04P = 0.98P = 0.04P = 0.62
Limits of agreement*−34, +38−13.2, +20.2−34.1, 38.6−7.6, + 11.1
SMFPercentiles: 50th (25, 75)
Left569 (385, 784)120 (89, 170)440 (287, 607)21.4 (18.6, 26.4)27.4 (23.6, 34.4)
Right547 (369, 773)119 (83, 172)433 (280, 593)22.1 (18.9, 26.3)29.0 (24.7, 34.6)
Test for left-right differenceP = 0.21P = 0.94P = 0.18P = 0.33P = 0.11
Limits of agreement*−138, 186−42, +63−116, +161−6.5, +9.1−8.1, +11.3
MLO views (246 women, 491 films)
ThresholdPercentiles: 50th (25, 75)
Left171 (135, 217)18.3 (9.5, 33.0)148 (109, 200)12.1 (5.7, 21.7)
Right170 (131, 213)20.3 (8.6, 32.9)146 (105, 191)12.9 (5.0, 20.4)
Limits of agreement*−32, +36−13.7, +21.4−33.0, +37.1−7.9, +11.9
Test for left-right differenceP = 0.02P = 0.71P = 0.03P = 0.37
SMFPercentiles: 50th (25, 75)
Left630 (460, 872)133 (95, 189)480 (341, 673)21.6 (18.1, 26.5)28.5 (23.8, 34.2)
Right625 (443, 867)134 (97, 191)483 (339, 667)22.0 (18.0, 26.9)28.9 (23.9, 35.5)
Limits of agreement*−167, +230−56, +97−143, +206−8.0, +12.6−10.4, +16.1
Test for left-right differenceP = 0.12P = 0.88P = 0.06P = 0.20P = 0.20
CC-MLO differences
ThresholdTest for CC-MLO differenceP = 0.03P = 0.84P = 0.01P = 0.19
SMFP < 0.001P < 0.001P < 0.001P = 0.58P = 0.40
• Abbreviations: CC, craniocaudal; MLO, mediolateral oblique; NA, not applicable.

• * Limits of agreement refer to the range in which 95% of left-right differences are expected to lie, calculated as mean difference ± 2 SD (difference).