Dual-energy tissue cancellation in mammography for improved detection of microcalcifications and neoplasms: A phantom study

Dual-energy mammography and the tissue-cancellation algorithm were applied to the problem of enhancing the detectability of calcifications and lesions in cluttered mammogram background. A multicomponent (plexiglass (PMMA), polypropylene (PP), water) tissue-equivalent breast phantom and a standard full-field digital mammography system operating in two of its standard operating modes (26 kVp, 40 mAs, Mo/Mo and 49 kVp, 6.3 mAs, Rh/Rh target/filter) were used. We studied to what extent the contrast between the tissue substitutes can be eliminated depending on the difference in their attenuation properties, and whether the obtained level of contrast cancellation is sufficient to unambiguously discriminate microcalcifications and inserts from the background. Mixed results were obtained. It was shown that the tissue-cancellation method can provide nearly perfect elimination of the background clutter (17-fold decrease in standard deviation) for homogeneous materials with close attenuation properties (PMMA and water) while increasing the contrast of a third material (PP, 1.7 times increase in contrast-to-noise ratio), thus facilitating its detection and delineation. However, canceling the contrast between materials with more different attenuation properties (PP and water) does not simultaneously lead to any significant enhancement of the contrast of a third material (PMMA), if its attenuation properties are close to those of either PP or water. Moreover, intrinsic inhomogeneity of the phantom constituents becomes important as it results in incomplete contrast cancellation and preservation of visually significant background clutter. Although contrast cancellation increased the signal-to-noise ratio of microcalcifications by about 33%, the relative contrast calcifications—background​ can diminish, making it possible for the remaining clutter to obscure the microcalcifications.