A design of mammography units using a quasimonochromatic x-ray source

In this article we present a mammography unit design using a parametric x-r adiation (PXR) source. We show that PXR can provide a fanned quasimonochrom atic x-ray beam that can be used to obtain mammography images of higher con trast and lower dose than those obtained from a conventional x-ray system. Changing the Bragg angle of the PXR crystal with respect to the electron be am changes the photon energy, improves image quality, and minimizes dose. M onte Carlo computer simulations are given that show that the PXR source wit h a 5% bandwidth gives a figure of merit close to that of the ideal monoene rgetic source and significantly higher than that of the filtered-x-ray-tube sources. In order to simultaneously obtain adequate flux and achieve bandw idths below 5%, we utilized an electron-beam energy of 35 MeV and an averag e current of 300 muA to 1 mA for 3 s (depending upon breast thickness and d ensity). Slits after the PX radiator are used to define both the spatial di stribution and the spectral bandwidth of the x-ray beam, which is scanned o ver the breast in approximately 3 s. A graphite crystal C (002) in the Laue geometry is utilized as the PX radiator. Lower electron-beam currents migh t be possible as higher efficiency PX or hybrid radiators become available. (C) 2001 American Institute of Physics.