Radiation Imaging with Pixel Detectors
J. Jakubek 1*
1 Institute of Experimental and Applied Physics, Czech Technical University in Prague
The history of imaging with penetrating radiation is more than century long. The main motivation for the usage of penetrating radiation for imaging is the possibility to visualize the internal structure of optically opaque objects. For this purpose it is necessary to use a suitable imaging sensor which is capable to detect the radiation and to record its properties. Traditionally the imaging detectors used (films, CCD or CMOS sensors) record the intensity of the transmitted radiation only. In this contribution it will be shown that also other radiation properties such as energy spectrum, angle of incidence and polarization can be used as independent modalities for image formation. These modalities can be used for better characterization of the object structure and its material composition.
Recent advances in semiconductor technology allow constructing highly efficient and low noise pixel detectors of ionizing radiation. Steadily improving quality of front end electronics enables fast digital signal processing in each pixel which offers recording more complete information about each detected quantum (energy, time, number of particles). All these features extend the applicability of pixel technology in different fields including imaging.
Most imaging techniques are based on image integration during a certain exposure time. Although the integration technique can be used with pixel detectors too, it is furthermore possible to operate such detectors in event-by-event mode recording complex information about each detected ionizing particle separately. This operation mode is enabled by fast digital data processing in each pixel and fast readout. Such list-mode measurement allows application of additional restrictions and performing more complex image reconstruction.
Several imaging applications of pixel detectors of Medipix type will be shown in this contribution. Among others they include high contrast energy sensitive X-ray transmission radiography, X-ray phase sensitive imaging, X-ray fluorescence imaging, ion transmission radiography and neutron imaging.