An Imaging Plate and storage phosphors for new radiation detectors

An Imaging Plate (IP) is an 'electronic film' for radiation, which is formed with plastic film coated with a photostimulable phosphor, BaFBr: Eu2+, as a radiation sensitive storage element. The IP has been mainly used in medical diagnosis and crystal structure analysis, and also used in life sciences, specially as a indispensable sensor at extremely low energy beta ray autoradiography with 3H and 14C. The application of the two-dimensional radiation detector is now spreading in the field of various nuclear radiation measurements. As the latent image is read out with photostimulated light induced by laser light scanning the one surface of the 50-150 μm thick IP phosphor plate, it has been long time thought that the readable information is limited only to store map of radiation dose density. It was found, however, that the IP has stored in it the radiation types, energies and stopping powers as well as the dose of the incident radiations. Up to this time, many proposals to extract the information of the radiation types and particle energies from the IP. The radiation 'electronic film' still monochromatic is expected to be developed to an everyday chromatic radiation one in near future. The IP radiation imaging with the particle identification and energy discrimination has been tried into practice in radiography, which realizes the usage of double labeled bio-tracers and/or an exclusive imaging of complex RI contamination, etc. A gamma-ray discrimination technique of a combination of a short time photo-bleaching and a somewhat long time restoration of image still remaining in IP through an oozing effect has been successfully applied to neutron radiography with Gd converter. Moreover, storage phosphors composed of light elements, such as KCl: Eu, have been found good for their low gamma-ray sensitivity. (J.P.N.)