Photostimulable phosphor

The flexible large area screen with photostimulable phosphor called the imaging plate, which temporarily stores the image induced by the ionizing radiation, e g. by X-rays, electrons or other charged particles ... 

Lanthanide luminescence apphcations have already reached industrial levels of consumption. Additionally, the strongly specific nature of the rare-earths energy emissions has also led to extensive work in several areas such as photostimulable phosphors, lasers (qv), dosimetry, and fluorescent immunoassay (qv) (33). 

Photostimulable phosphors based on Eu + doped BaBrP are used in area detector systems in X-ray crystallography and medicine. 

For all detector types, the transfer of energy to the detector material as the photoelectrons and recoil electrons slow down occurs through excitation or ionization of electrons in neighboring atoms within the detector structure. What occurs next depends on the specific molecular structure of the detector. We can distinguish between structures such as noble gases, photoconductors, fluorescent phosphors, and photostimulable phosphors. 

A photostimulable phosphor system for digital mammography was originally introduced commercially by Fuji Film. Several other PSP systems are now available and these are listed in Table 2.2. The dels are of a nominal size of 50 pm. 

Fig. 2.12. Photostimulable phosphor system (a) mechanism of the PSP, (b) double-side d readout to increase efficiency (from Digital Mammography, eds. ED Pisano, MJ Yaffe, CM Kuzmiac. Lippincott, Williams and Wilkins, a Walters Kluwer Company, 2004. Used with permission)...

To increase sensitivity and improve SNR, some photostimulable phosphor system manufacturers have refined their plate technology to reduce laser scattering and increased the efficiency of light collection by reading from both the top and bottom surfaces of the phosphor plate (Fig. 2.12b). 

In photostimulable phosphor systems, the spread of Ught from its point of emission does not affect spatial resolution. The spatial localization is determined initially by the size of the laser spot that is used to read out the signal. As the laser Ught travels through the phosphor, it causes electrons trapped in the phosphor during the X-ray exposure to be freed from the traps. Some of these tiien produce Ught The emitted Ught is collected by an optical system and a photodetector (Fig. 2.17a). 

Fig. 2.17. Resolution loss in a photostimulable phosphor, (a) In the ideal system all emitted light arises from the point of X-ray interaction, (b) scattering of readout laser light within the phosphor material causes blur...

Meijerink A, Blasse G, Straye L (1989) A new photostimulable phosphor Eu -activated barium bromosilicale (Ba5Si04Br6). Matra Chem Phys 21 261... 

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