Production of quasi-monochromatic X-rays via crystal array for mammography

Quasi-monochromatic X-ray beams have been produced in the mammographic energy range. The source is based on a conventional tungsten anode X-ray tube and an array of graphite mosaic crystals as monochromator. An optical system consisting of an array of three crystals (2.8 x 3.0 cm2) has been assembled so as to produce in the image plane an irradiation field obtained with adjacent reflected beams. At 18 keV the beam has a field size of about 6.0 X 8.0 cm2, with a percentage energy resolution of 13% (FWHM). The field size is limited by the crystal dimension along the vertical direction and by the energy spread and the number of crystals along the other one. Radiographic images of a test object have been obtained both with a screen/film combination and a digital detector. Techniques to eliminate the spatial non- uniformities have been applied. Field non-uniformities have been removed with a proper correction procedure: 'flat fielding' for a digital imaging system, or scanning technique for screen/film combination