Direct and indirect detectors for X-ray photon counting systems

Abstract

Most currently available X-ray or gamma ray imaging detectors are based on energy integration over a certain period of time. We have been developing X-ray and gamma ray detectors based on the photon counting (with energy determination) concept using both direct and indirect radiation conversion, together with associated application-specific integrated circuits (ASICs). As an alternative to our ASIC design approach, we are also exploiting the potential of state-of-the-art silicon photomultipliers (SiPMs) and discrete electronics. In this paper we discuss the advantages and disadvantages of these two approaches and we report our latest results on our ASIC design efforts and our achievements on SiPMlCsI:TI detector configurations. We will also discuss the potential uses and advantages that each offers to applications in medicine, imaging, homeland security and industry.

Spectral X‐ray computed micro tomography: 3‐dimensional chemical imaging

“…In contrast, a PCD uses a semiconductor crystal such as CdTe, CdZnTe, Se or Si that directly converts the incoming X‐ray photon into an electric charge. Therefore, it is also called direct detection [ 55 ] . The detector consists of a single semiconductor crystal, two electrodes, and the readout electronics or application‐specific integrated circuit (ASIC) (Figure 2).…”

Performance of low-cost X-ray area detectors with consumer digital cameras

“…High energy indirect detection involves the use of a phosphor or scintillator to convert incident X-ray photons to visible light, which is coupled to a visible light detector via lenses or fiber-optics. These X-ray detectors operate in the energy integrating mode [1], where the energy of the incident radiation on the detector is digitized to form images. Consumer cameras are low-cost options that can be focused onto the phosphor layer with lenses.…”

Tutorial on X-ray photon counting detector characterization

“…The absorption efficiency of X-ray photons in inorganic crystalline scintillators is high due to the large average atomic numbers such as in sodium iodide (NaI, Z=11/53) and bismuth germanium oxide (BGO, Z=83/32/8) [23]. Considering the high absorption efficiency and the capability of being manufactured into a large scale, inorganic scintillator based photon counting detectors are typically applied in nuclear medicine applications such as positron emission tomography (PET) [23, 28]. Conventional scintillator based detectors are also used in computed tomography (CT) scanners but are operated in current mode (energy-integrating) rather than photon counting mode (pulse mode).…”

“…Similar to gas based photon counting detectors, semiconductor based photon counting detectors directly convert X-ray photons into electrical charges, and therefore are regarded as direct detectors [28, 29]. As silicon (Si, Z=14) is a well understood semiconductor and homogeneous large Si wafers are easily available, Si has been widely used as sensor material for photon counting detector.…”