The imaging plate(developed by Fuji Photo Film Co.) is a useful application of photostimulated phosphor to radiation detection. Originally, the plate was intended to replace Xray films. However, the excellent performance of the plate allow to use in the fields of electron-microscopy, autoradiography, X-ray diffraction and neutron imaging. Furthermore, the plate is going to be applied to two-dimensional radiation detection. We should improve few flaws of the plate and accumulate the results of studies before the take off of the application.

  We have studied the PSL and its fading characteristics of various photostimulable phosphor materials, such as alkali halide and II－VI compound phosphors. We found that europium-doped potasium bromide (KBr:Eu) phosphor exhibited an excellent fading characteristics. In the paper, the mechanism of the fading characteristics have also been discussed.

  Photostimulated luminescence phenomena have been observed in reduced rare earth ions i.e. Ce³⁺ and Eu²⁺, doped glasses. When the X-ray irradiated glasses were excited by a He-Ne laser (633 nm), photostimulated luminescence due to the 4f-5d transition of Ce³⁺ and Eu²⁺ ions was observed. X-ray absorption spectra of glasses X-ray irradiated for various durations were measured in order to examine the valence state and microstructure of the rare earth ions. In comparison with the mechanism of photostimulated luminescence in BaFBr:Eu²⁺, the luminescence is proposed to result from the photostimulated recombination of holes and electrons at traps which leave electrons in a long-lived excited state. These glasses may be promising materials as two-dimensional imaging sensors of X-ray.

  BaFBr:Eu²⁺ is a remarkable material in its efficient ability of X-ray image recording. Although the ability has been studied for this decade, the mechanism for the storage and readout has not been fully understood. The optical properties of the electron and hole traps as well as the bulk crystal of BaFBr are discussed.

  A compact imaging plate readout system for X-ray diffraction studies on the mechanical behavior of materials has been constructed. A He-Ne laser beam transmitted through an optical fiber is focused on an imaging plate. Both linear and logarithmic amplifiers can be used as a preamplifier. The preamplifier output is integrated for a sampling period of 38 μs which corresponds to the 100 μm reading. Experiments using 5.6 keV X-rays have been carried out to obtain the characteristics of the system. Applications on the field of material strength are also presented.

  Photostimulated luminescence (PSL) of an imaging plate (BAS-UR, Fuji Film Co.) is measured using a home made readout instrument. The PSL of the plate is compared for a unit dose of three kinds of radiation; α, β, and γ -rays. It is shown that the response for a unit absorbed dose of γ -rays is larger than that of α and β -rays. Measurements are also extended to a fading characteristic of the plate and the result reveals that fading curves are composed of two (fast and slow) components irrespective of radiation sources used for the primary excitation.

  The imaging plate (IP, here BaFBr:Eu²⁺ based imaging plate) is well known to have many striking performances of two-dimensional radiation detection. We pointed out that an arrangement of some kind of ROI (region of interest) windows on particle type and/or particle energy in its imaging can highly improve the S/N (signal-to-noise ratios) and give us a new world of truly exclusive radiographies.

An outline of particle identification and energy determination with the imaging plate was given. A trial construction of a new type of IP reader proving the identification was shown.

  We have developed the separation method of alpha ray image and gamma ray image by using the imaging plate(IP). The IP which has been read out the first image by the image reader is annealed at 50 degrees C for 2 hours in a drying oven and is read once more by the image reader. Subtracting k times of the second image from the first image, we can get the alpa image. Here, k is the annealing ratio which is defined as PSL dencity of gammga ray irradiated area of the first measurement to the one of the second measurement.

  We have developed an imaging plate neutron detector (IP-ND). Properties and optimization of the IP-ND were examined experimentally by changing a kind of the neutron converter, the molar ratio of neutron converter to photostimulated luminescence (PSL) material and the thickness of the IP-ND.

  The distinctive features of the IP-ND are applicable for neutron diffraction experiments from bio-macromolecules as well as powder diffraction and neutron radiography.

  It is possible to measure the geometrical distribution of extremely low level natural radioactivity contained in vegetables, meat etc. by utilizing a very high sensitivity of Imaging Plate for radiations. For this purpose, however, reduction of background (BG) radiations is necessary by using a shielding box of, for example, lead with a thickness of ～10cm. Monte-Carlo simulation shows that BG image is given by electrons emitted from the inner surface of the shielding box under the interaction of γ-rays transmitted through the box rather than by the γ-rays themselves. In the case of lead box, the inner surface has to be covered with other materials to cut the β-rays emitted from Bi-210 contained in lead. In the exposure of vegetables, meat etc. for 20 days or more, rotting, oozing-out of water, shape variation of the specimens must be avoided. The effect of C-14 β-rays in making the latent image is negligibly small compared with K-40 β-rays.

  Since the the superior characteristics of Imaging Plate (IP) (high sensitivity, wide dynamic range, and sensitivity linearity) had been shown fully effective also for electrons, the IP is now widely used in the field of transmision electron microscopy (TEM). Recently, high-resolution type IP for TEM, which has 25μm-size pixels, has been developed and commercialized, thus bringing the IP into a wide use in the field of TEM.

  In this article, the fundamental characteristics of the 25μm-pixel IP and its examples of application to quantitative image analysis are introduced.

  Recent progress in imaging plate (IP) system al low us to analyze autoradiographic images quantitatively. In the ”whole-body auto radiography”, a method clarify the distribution of radioisotope or labeled compounds in the tissues and organs in a freeze-dried whole-body section of small animals such as rats and mice, the sections are pressed against a IP for exposure and the IP is scanned by Bio-Imaging Analyzer (Fuji Photo Film Co., Ltd) and a digital autoradiographic image is given. Quantitative data concerning the activity in different tissues can be obtained using an isotope scale as a reference source. Fading effect, application of IP system for distribution of receptor binding ARG, analysis of radio-spots on TLC and radioactive concentration in liquid such as blood are also discussed.