This diagram shows the geometry of a phase-contrast mammography system. Phase perturbations due to breast refractive index discontinuities manifest as intensity variations at the detector.
The energy-dependent x-ray refractive index (n = 1 − δ + iβ) properties of breast tissue shown here were derived from the XCOM database and the elemental compositions shown in Table I.
This flow chart shows the steps necessary to adapt the CLB model for PCM and compute propagated detector-plane intensity data.
This figure shows the effect of anode spot size on edge enhancement in PCM. The image on the left (and inset line plot through the center row) shows the ideal intensity, with an infinitely small spot size, due to an 80-μm-diameter calcification object in an adapted CLB breast background under a Konika–Minolta system geometry (Ec = 25 keV, E = 25 keV). The middle and right images have been blurred to account for 20 μm and 50 μm anode spot sizes, respectively. Images are displayed in Hounsfield units.
The background intensity data on the left is the detector-plane intensity due to the propagation of a monoenergetic wavefield derived from a CLB model (Konica-Minolta system geometry, Ec = 25 keV, E = 25 keV, 49 μm pixel size; intensity is displayed as percent transmission). The image on the right shows the empirically computed noisy background covariance estimate K for polyenergetic background data (28 kVp Mo source, 30 -μm-thick Mo filter, 100 μm anode spot size, and 100 mRad mean glandular dose).
As an example of the methods described in this work, the effect of the source spot size on calcification detectability was studied for the Konica-Minolta system geometry (denoted KM) and a typical mammography geometry (denoted M). These results show that, although the typical Konica-Minolta system configuration (source size of 100 μm) may offer somewhat better performance than mammography, improved detectability can be achieved when the source spot size is further reduced. Note that the mean glandular dose was held constant at 100 mRad for these studies and that imaging times varied.
Tissue properties, derived from published data,17–22 used to compute the complex refractive index of the simulation model. These data are derived from published values.
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