History and future of radiation imaging with single quantum processing pixel detectors

This introductory article treats aspects of the evolution of early semiconductor detectors towards modern radiation imaging instruments, now with millions of signal processing cells, exploiting the potential of silicon nanotechnology. The Medipix and Timepix assemblies are among the prime movers in this evolution. Imaging the impacts in the detecting matrix from the individual ionizing particles and photons can be used to study these elementary quanta themselves, or allows one to visualize various characteristics of objects under irradiation. X-ray imaging is probably the most-used modality of the latter, and the new imagers can process each single incident X–photon to obtain an image with additional information about the structure and composition of the object. The atomic distribution can be imaged, taking advantage of the energy-specific X-ray absorption. A myriad of other applications is appearing, as reported in the special issue of this journal. As an example, in molecular spectroscopy, the sub-nanosecond timing in each pixel can deliver in real-time the mapping of the molecular composition of a specimen by time-of-flight for single molecules, a revolution compared with classical gel electrophoresis. References and some personal impressions are provided to illuminate radiation detection and imaging over more than 50 years. Extrapolations and wild guesses for future developments conclude the article.