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Grid and slot scan scatter reduction in mammography: comparison by using Monte Carlo techniques
John M Boone1, J Anthony Seibert, Cha-Mei Tang
1Department of Radiology, University of California, Davis, 4701 X St, Research Imaging Laboratory, UC Davis Medical Center, Sacramento, CA 95817, USA. jmboone@ucdavis.edu
Purpose:
To evaluate a comprehensive array of scatter cleanup techniques in mammography by using a consistent methodology.
Materials And Methods:
Monte Carlo techniques were used to evaluate the Bucky factor (BF) and the contrast improvement factor (CIF) for linear and cellular grids and for slot scan and scanning multiple-slot assembly (SMSA) systems.
Results:
For a 28-kVp molybdenum anode-molybdenum filter spectrum with a standard detector and a 6-cm-thick 50% adipose-50% glandular breast phantom, slot scan techniques delivered an ideal BF. For slot widths greater than 4 mm, however, the CIF was lower than that achieved by the high-transmission cellular grid with a grid ratio of 3.8:1. A tungsten-septa air-interspaced cellular grid with a 4:1 grid ratio outperformed the high-transmission cellular grid in both BF and CIF. The SMSA was shown to be efficacious when 4-mm-wide slots were separated by at least 20 mm. In comparison with the literature, 3.6% agreement was achieved with other Monte Carlo studies, 3.3% with an experimental study that used a digital detector, and 13%-29% agreement was demonstrated in comparison to film-based experimental studies.
Conclusion:
With use of consistent methods for comparison, cellular grids were shown to substantially outperform linear grids but have slightly higher BFs compared with that of slot scan geometries at the same CIF.