Anatomical background noise power spectrum in differential phase contrast and dark field contrast mammograms.

PURPOSE In x-ray absorption mammography, it has been found that the anatomical background noise can be characterized by a power law dependence on the spatial frequency, NPSa(f) ≈ αf(-β). In this letter, the authors present the first experimental results of the corresponding exponents, β, for differential phase contrast (βDPC) and dark field contrast (βDF) mammography. METHODS A grating-based x-ray multicontrast imaging acquisition benchtop system was used to simultaneously acquire mammograms with three different contrast mechanisms from 15 cadaver breasts under the same x-ray data acquisition conditions. The cadaver breasts were imaged in the coronal plane. The authors' experimental implementation of the well documented method [Burgess, Jacobson, and Judy, Med. Phys. 28, 419-437 (2001)] to extract the exponent β was first validated using anonymized clinical mammograms. Experiments were then used to determine β for the three types of mammograms for each cadaver breast acquired with our multicontrast imaging system: absorption contrast mammogram (βAbs.), differential phase contrast mammogram (βDPC), and dark-field contrast mammogram (βDF). RESULTS The measured β values, acquired in the coronal plane with the benchtop multicontrast imaging system are βAbs. = 3.61 ± 0.49, βDPC = 2.54 ± 0.75, and βDF = 1.44 ± 0.49 for absorption, differential phase, and dark field mammogram, respectively. CONCLUSIONS The β values for differential phase contrast and dark field mammography are significantly lower than the measured value of β for the corresponding absorption contrast mammograms. The greatly reduced β value of the anatomical background noise in differential phase contrast and dark field mammograms may suggest potentially improved diagnostic performance for certain types of breast cancer imaging tasks.