VBD evaluation from DM.—

The commercially available Quantra (version 2.1) (11) and Volpara (version 1.5.3, Volpara Health Technologies) (9) software packages can assess VBD from raw DM images. Using the image pixel intensities, known x-ray attenuations for dense versus fatty tissue, and the Digital Imaging and Communications in Medicine, or DICOM, header values for breast thickness and compression, Quantra and Volpara approximate the thickness of adipose versus fibroglandular tissue within each pixel of the DM image. In both cases, summing the approximations of dense pixel volumes provides DV, and normalizing DV by the total breast volume gives VPD%. We used the DV and VPD% generated by Quantra (DV_DM-Q and VPD%_DM-Q) and Volpara (DV_DM-V and VPD%_DM-V) from both raw DM views available for each woman.