Digital autoradiography with a Medipix2 hybrid silicon pixel detector

A digital imaging system for beta and gamma autoradiography has been realized. It is a hybrid pixel detector based on a Medipix2 circuit (a single photon counting chip), developed at CERN in the framework of the Medipix2 European collaboration, as a successor of the Medipix1 chip. Medipix2 is realized in 0.25-/spl mu/m CMOS technology; it has a sensitive area of 14 /spl times/ 14 mm/sup 2/ and a pixel pitch of 55-/spl mu/m and is bump bonded to a 300-/spl mu/m-thick silicon pixel detector. A test of this imaging system for digital autoradiography, with a detection threshold of about 6 keV, shows a noise in the order of 10/sup -3/ cps/mm/sup 2/, a minimum detectable activity of 0.32 Bq in 14 h for /sup 3/H, and 0.012 Bq in 10 h for /sup 14/C. A preliminary spatial resolution test for /sup 14/C gives a full-width at half-maximum resolution of about 80 /spl mu/m. Real-time images of /sup 3/H, /sup 14/C, /sup 125/I autoradiographic microscales are shown, and a comparison with existing experimental devices is presented.