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Single Mo target, Mo / Rh, or Mo / W bi-track targets with corresponding Mo and Rh filters have provided optimal
target / filter combinations for traditional screen / film systems. In the advent of full-field digital mammography, similar
target / filter combinations were adopted directly for digital imaging systems with direct and indirect conversion based
detectors. To reduce the average glandular dose while maintaining the clinical image quality of FFDMs, alternative
target / filter combinations have been investigated extensively to take advantages of the digital detectors with high
dynamic range, high detection dose efficiency, and low noise level. This paper reports the development of a digital
FFDM system that is equipped with single tungsten target and rhodium and silver filters. A mathematical model was
constructed to quantitatively simulate x-ray spectra, breast compositions, contrast objects, x-ray scatter distribution, grid
performance, and characteristics of a-Se flat panel detector. Computer simulations were performed to select kV/filter for
different breast thickness and breast compositions through maximizing the contrast object detection dose efficiency. A
set of phantom experiments were employed to optimize the x-ray techniques within the constraints of exposure time and
required dose levels. A 50-micrometer rhodium filter was applied for thin and average breasts and a 50-micrometer
silver filter for thicker breasts. To meet our design requirements and EUREF protocol specifications, we finely adjusted
x-ray techniques for 0.45, 0.75, 1.0, 1.35 mGy dose modes with regards to ACR phantom scoring and PMMA phantom
SNR/CNR performance, respectively. The optimal x-ray techniques significantly reduce average glandular dose while
maintaining imaging performance.
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