Anatomical landmark on axial, precontrast fat-suppressed and nonfat-suppressed images. The fat-suppressed imaging sequence was a 3D gradient echo with SPAIR fat-suppression, with TR = 6.20 ms, TE = 1.26 ms, flip angle = 12°, matrix size = 480 × 480, FOV = 31–38 cm, slice thickness = 1 mm, and 160 axial slices. The nonfat-suppressed sequence was a 2D turbo spin-echo with TR = 800 ms, TE = 8.6 ms, flip angle = 90°, matrix size = 480 × 480, FOV = 31–38 cm, slice thickness = 2 mm, and 84 axial slices. The spatial location 5 mm posterior to the dorsal margin of the sternum, indicated by the arrow, is used as the point through which a horizontal line is drawn (a). The nonbreast tissue is excluded (b), resulting in defined breast tissue (c). The contrast between breast tissue and the pectoral muscle on both fat-suppressed and nonfat-suppressed images is very clear, showing reverse signal intensities, which allows a successful segmentation to remove the pectoral muscle on both sets of images.
An example of density segmentation on a “Central” type breast of a 39-year-old patient, showing confined fibroglandular tissue surrounded by fatty tissue. The contrast between fibroglandular tissue and fatty tissue is strong on both sets of images. On nonfat-suppressed images, the fibroglandular tissue is dark; on fat-suppressed images, the fibroglandular tissue is bright and nearly mirrored and reversed. Some subtle differences exist on the segmented fibroglandular tissues, but the quality is acceptable on both sets of images without obvious errors. Compared with the original image, the downsampled image is blurred, yet the contrast remains very strong for segmentation. The measurement results are listed in Table II.
An example of density segmentation on an “Intermingled” type breast of a 31-year-old patient, showing mixed fibroglandular tissue and fatty tissue. The segmented fibroglandular tissue region is slightly larger on fat-suppressed images. Nevertheless, the quality is acceptable on both sets of images without obvious errors. Compared with the original image, the downsampled image is blurred, yet the contrast remains very strong for segmentation, and the segmentation results are similar. The measurement results are listed in Table II.
Spearman’s Rho between measurements from fat-suppressed and nonfat-suppressed images for (a) breast volume, (b) fibroglandular tissue volume, and (c) percent density. The parameters measured from the fat-suppressed sequence are on the y-axis; from the nonfat-suppressed sequence are on the x-axis. They are highly correlated with p < 0.001. The best-fit line passing through the origin is plotted on the figure, with a slope of 1.0019 for breast volume, 1.0276 for fibroglandular tissue volume, and 1.0247 for percent density. The dotted black line indicates the unity line representing 1:1 correlation. The least squares regression line lies close to the unity line.
Breast volume, fibroglandular tissue volume and percent density measured on fat-suppressed and nonfat-suppressed images in different groups.
Parameters measured on images at original and reduced spatial resolution for cases shown in Figs. 2 and 3.
Parameters measured on images at original and reduced spatial resolution.
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