THE DIGITAL MAMMOGRAPHY PROGRAM AT THE SR LIGHT-SOURCE IN TRIESTE

A synchrotron radiation beamline devoted to medical imaging has been b uilt by the SYRMEP collaboration at Elettra in Trieste, Italy, and is now in operation. The SYRMEP imaging system is based on the combinatio n of a monochromatic, laminar X-ray beam, with a laminar, high-efficie ncy pixel silicon detector. To image soft tissue, including small, low -contrast details, as in mammography, beam energies should be chosen i n the range from 15 keV to 30 keV and the detector should be capable o f single-photon counting. The SYRMEP beamline originates from a bendin g magnet light port and consists basically of a Be window, a slit syst em and a Si(1,1,1) crystal monochromator. The experimental area is equ ipped with a radiation flux monitor, a sample movement stage, and a po sitioning system holding the silicon detector. Images are obtained by keeping the detector stationary with respect to the beam and by scanni ng the sample through the beam itself. The current detector is a linea r array of 200x300 mu m(2) pixels, each coupled to its electronic coun ting chain on a custom VLSI read-out chip. We present a summary of bea m studies, and digital images of standard RMI 160 and RMI 180 Ackerman n Mammographic phantoms. Results show the high contrast resolution and the large dynamic range which constitute the defining characteristics of the SYRMEP imaging system.