Method for Dual High Energy X-ray Imaging with Flat Panel Detectors
نویسندگان
چکیده
Dual-energy X-ray imaging in the keV range is a well-known technique e.g. used in baggage scanning. It requires two measurements at different energies and/or detector efficiencies and allows displaying material properties as the effective atomic number and mass density. The method thus provides the information allowing identifying illicit materials such as explosives and contraband or high-Z material used for shielding of radioactive or fissile material. Baggage scanners typically operate with 160 kVp X-ray sources, providing photons of energies between approximately 10 keV and 160 keV. For large objects as complete cars or sea freight containers for example, much higher photon energies are required to penetrate the object, i.e. in the range of a few MeV. The keV-dual-energy imaging exploits the energy dependence of the attenuation due to photoelectric and Compton effects. MeV-dual-energy imaging relies on pair production and Compton effect, which is more challenging since the energy dependence differs less between these effects. Due to the higher proportion of scattered radiation and the lower efficiency of flat panels, usually line detectors combined with a heavily collimated fan beam are used. However flat panel detectors offer a higher resolution and cover a twodimensional area which allows for shorter scan times. We employed a method using a ratio of the intensities in both images of different X-ray energies, and could show that materials differing in Z can be distinguished. We introduce the principles of the method and present first measurements from our 9 MV linear accelerator (LINAC) test facility.
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