14C autoradiography with an energy-sensitive silicon pixel detector

Abstract

The first performance tests are presented of a carbon-14 (14C) beta-particle digital autoradiography system with an energy-sensitive hybrid silicon pixel detector based on the Timepix readout circuit. Timepix was developed by the Medipix2 Collaboration and it is similar to the photon-counting Medipix2 circuit, except for an added time-based synchronization logic which allows derivation of energy information from the time-over-threshold signal. This feature permits direct energy measurements in each pixel of the detector array. Timepix is bump-bonded to a 300 νm thick silicon detector with 256 × 256 pixels of 55 νm pitch. Since an energetic beta-particle could release its kinetic energy in more than one detector pixel as it slows down in the semiconductor detector, an off-line image analysis procedure was adopted in which the single-particle cluster of hit pixels is recognized; its total energy is calculated and the position of interaction on the detector surface is attributed to the centre of the charge cluster. Measurements reported are detector sensitivity, (4.11 0.03) × 10-3cps mm-2kBq-1g, background level, (3.59 0.01) × 10-5cps mm-2, and minimum detectable activity, 0.0077 Bq. The spatial resolution is 76.9 νm full-width at half-maximum. These figures are compared with several digital imaging detectors for14C beta-particle digital autoradiography. © 2011 Institute of Physics and Engineering in Medicine.