Design considerations of a slot scintillation detector for digital mammography

We are currently developing a scanning slot digital mammography system using a tin loaded plastic scintillating fiber screen (SFS) which permits high detector x-ray absorption efficiency and excellent spatial resolution. We investigated the dependence of zero spatial frequency detective quantum efficiency, DQE(0), and modulation transfer function, MTF(f), on the thickness and scintillating fiber diameter of a 7.5% by weight tin loaded SFS. DQE(0) values of a 20 mm thick SFS were > 80% for the x-ray energies used in mammography. MTF(f) values showed negligible variance over SFS thickness from 10 to 25 mm and were found to be > 60% for the SFS made of 20 mu m scintillating fibers. The results show that high DQE(0) and spatial resolution can be achieved with a 20 mm thick SFS composed of 20 mu m scintillating fibers.