Evaluation of a photon counting X-ray imaging system

A digital imaging system has been developed for mammography using silicon strip detectors operated in a pulse-counting mode and configured in a scanned slit geometry. Almost 100% of the photons are absorbed in the sensor, the scatter rejection is very efficient and the image formation is nearly optimal since each X-ray is processed individually. The result is a very dose-efficient system. In this paper we present measurements that verify that the performance of the read-out electronics is sufficient to count photons at high rates with high quantum efficiency (QE) and a charge collection efficiency (CCE) that does not limit the dose efficiency. The spatial resolution of the system was measured to provide a modulation transfer function (MTF) of approximately 0.5 at a spatial frequency 10 1p/mm. Images of a mammography phantom were recorded experimentally to test overall system performance