CALCULATED MAMMOGRAPHIC SPECTRA CONFIRMED WITH ATTENUATION CURVES FORMOLYBDENUM, RHODIUM, AND TUNGSTEN TARGETS

A model for calculating mammographic spectra independent of measured d ata and fitting parameters is presented. This model is based on first principles. Spectra were calculated using various target and filter co mbinations such as molybdenum/molybdenum, molybdenum/rhodium, rhodium/ rhodium, and tungsten/aluminum. Once the spectra were calculated, atte nuation curves were calculated and compared to measured attenuation cu rves. The attenuation curves were calculated and measured using alumin um alloy 1100 or high purity aluminum filtration. Percent differences were computed between the measured and calculated attenuation curves r esulting in an average of 5.21% difference for tungsten/aluminum, 2.26 % for molybdenum/molybdenum, 3.35% for rhodium/rhodium, and 3.18% for molybdenum/rhodium. Calculated spectra were also compared to measured spectra from the Food and Drug Administration [Fewell and Shuping, Han dbook of Mammographic X-ray Spectra (U.S. Government Printing Office, Washington, D.C., 1979)] and a comparison will also be presented. (C) 1998 American Association of Physicists in Medicine.