A high efficiency single photon counting silicon matrix for position sensitive X-ray detection

The SYRMEP collaboration (Synchrotron Radiation for Medical Physics) is developing a novel imaging device to be used with a laminar monochromatic synchrotron radiation X-ray beam for applications in digital mammography. Its main components are silicon microstrip detectors and a dedicated VLSI readout chip based on the single photon counting concept. The innovative geometry-several overlapped detectors with strips parallel to the beam direction-determines a matrix of pixels, each of them having an area of 200/spl times/300 /spl mu/m/sup 2/, which can detect up to 10/sup 6/ photons/(mm/sup 2/ s) with 90% efficiency at 25 keV. Front-end and readout electronics are expandable in a modular fashion and can be coupled to successive receptor versions with increasing number of channels, while a VME based DAQ system offers full testing facilities. In our view this system is providing specific and original contributions to digital mammography but it could also be useful in other modern radiology fields.