Applications of avalanche multiplication in amorphous selenium to flat panel detectors for medical applications

A new concept of an indirect conversion flat panel detector utilizing avalanche multiplication phenomena in amorphous selenium (a-Se) is described. It is shown that high avalanche multiplication gain of 1,000 can be achieved for 35 μm thick a-Se layer. Combined with high quantum efficiency of charge photogeneration for peak emission from the CsI scintillator (almost unity) this significantly improves low dose detector performance. The avalanche gain dependence on both, applied electric field and photoconductor layer thickness is analyzed giving the possibility to program the gain (from 1 to 1,000) by adjusting applied field prior to exposure. This provides wide dynamic range required for the variety of clinical and biomedical applications.