PubMed · 5114344
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G Kühn. 1971. [Technical novelties from Picker].. https://pubmed.ncbi.nlm.nih.gov/5114344/
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A novel x-ray source for mammography application is being investigated. Quasimonochromatic x rays have been produced via Bragg diffraction with a W-anode x-ray tube and a graphite mosaic crystal array. The system provides 18 keV x rays with an energy resolution deltaE/E approximately equals 0.12. A thorough analysis of the spatial resolution of the system has been performed in order to understand and quantify the effect of the introduction of an active optical element such as a mosaic crystal in the x-ray path. The focal spot of the source and its emission properties have been studied by using the slit camera method. Experiments have shown that the introduction of a mosaic crystal in the optical path modifies the resolution properties of the Bragg diffraction-based radiography system. Along the direction perpendicular to the diffraction plane the resolution properties of the imaging system mainly depend on the x-ray tube focal spot size and position. Along the diffraction plane the focal spot size depends on mosaic characteristics and on the geometrical setup. Hence, it could be modified by setting the appropriate experimental conditions.
OBJECTIVE: The United States Food and Drug Administration implemented federal regulations governing mammography under the Mammography Quality Standards Act (MQSA) of 1992. During 1995, its first year in implementation, we examined the impact of the MQSA on the quality of mammography in North Carolina. MATERIALS AND METHODS: All mammography facilities were inspected during 1993-1994, and again in 1995. Both inspections evaluated mean glandular radiation dose, phantom image evaluation, darkroom fog, and developer temperature. Two mammography health specialists employed by the North Carolina Division of Radiation Protection performed all inspections and collected and codified data. RESULTS: The percentage of facilities that met quality standards increased from the first inspection to the second inspection. Phantom scores passing rate was 31.6% versus 78.2%; darkroom fog passing rate was 74.3% versus 88.5%; and temperature difference passing rate was 62.4% versus 86.9%. CONCLUSION: In 1995, the first year that the MQSA was in effect, there was a significant improvement in the quality of mammography in North Carolina. This improvement probably resulted from facilities' compliance with federal regulations.
The purpose of this project was to quantify reciprocity law failure (RLF) for mammography screen-film systems. Three widely used screen-film systems were evaluated: the Kodak MinR 2000 system. Fuji UM Mammo Fine screen and Fuji UM MA HC film, and Agfa MR Detail screen and Agfa Mammoray MR5 film. The logit algorithm that linearizes logistic curve shapes was utilized to characterize film sensitometric response. Different values of mammographic phantom thickness, tube current, and kVp were used to vary screen-film exposure rates. RLF was quantified by examining the dependence of logit parameters (maximum and minimum film density, curve shift, and slope) on exposure rate. The shift of the logit curve was found to be a good indicator of the screen-film system speed, while the slope of the logit curve is affected by the RLF. RLF leads to changes in film contrast as well as speed. For the range of exposure rates measured (50-fold), screen-film contrast and speed varied by factors of 2 and 3.5, respectively. Film contrast decreased as exposure rate increased. The greatest changes were observed with the Kodak MinR 2000 screen-film system.