This work investigated the effect of the grid-less acquisition mode with scatter correction software developed by Siemens Healthcare (PRIME mode) on image quality and mean glandular dose (MGD) in a comparative study against a standard mammography system with grid. Image quality was technically quantified with contrast-detail (c-d) analysis and by calculating detectability indices (d’) using a non-prewhitening with eye filter model observer (NPWE). MGD was estimated technically using slabs of PMMA and clinically on a set of 11439 patient images. The c-d analysis gave similar results for all mammographic systems examined, although the d’ values were slightly lower for the system with PRIME mode when compared to the same system in standard mode (-2.8% to -5.7%, depending on the PMMA thickness). The MGD values corresponding to the PMMA measurements with automatic exposure control indicated a dose reduction from 11.0% to 20.8% for the system with PRIME mode compared to the same system without PRIME mode. The largest dose reductions corresponded to the thinnest PMMA thicknesses. The results from the clinical dosimetry study showed an overall population-averaged dose reduction of 11.6% (up to 27.7% for thinner breasts) for PRIME mode compared to standard mode for breast thicknesses from 20 to 69 mm. These technical image quality measures were then supported using a clinically oriented study whereby simulated clusters of microcalcifications and masses were inserted into patient images and read by radiologists in an AFROC study to quantify their detectability. In line with the technical investigation, no significant difference was found between the two imaging modes (p-value 0.95).
This work investigated image quality as a function of PMMA thickness on a variety of mammography systems. Image quality was quantified by calculating detectability (d’) using a non-prewhitening with eye filter model observer (NPWE) from routinely acquired quality control (QC) data of twelve digital radiography (DR) systems. The sample of systems included two mammography devices equipped with the Siemens PRIME upgrade and one system with the Claymount SmartBucky detector. The d’ data were calculated for a 0.1 and 0.25 mm diameter gold discs using images of homogeneous PMMA (thickness from 2 to 7 cm), all from the routinely performed AEC test. The GE Essential systems had the highest d’ values for low thicknesses and the lowest d’ values for high thicknesses. The Hologic Selenia Dimension systems had the most constant detectability curve, ensuring high d’ values at high thicknesses. This was achieved by increasing the mean glandular dose (MGD) at higher thicknesses compared to the other systems. The Siemens PRIME and the Claymount system detectability results were comparable to the standard FFDM systems. Mean glandular dose at 5, 6 and 7 cm PMMA and gold threshold thickness at 5 cm PMMA were also evaluated. The Claymount system had a high (but acceptable) threshold gold thickness (T) compared to the other systems. This was probably caused by the low dose at which this DR detector operates. Results of NPWE d’ and CDMAM analysis showed the same trends.
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