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SU‐FF‐I‐156: Unerasable Latent Images Observed in Computed Radiography and Their Complete Erasing
Author(s) -
Ohuchi H
Publication year - 2009
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3181277
Subject(s) - latent image , psl , luminescence , ultraviolet , irradiation , materials science , optics , photostimulated luminescence , ultraviolet light , fluorescence , optoelectronics , computed radiography , physics , computer science , artificial intelligence , mathematics , image (mathematics) , geometry , nuclear physics , image quality
Purpose: Some unexpected effects in Computed Radiography (CR) have become known, i.e., the phenomena of unerasable and reappearing latent images, particularly for a film irradiated at high dose and/or a subsequently irradiated film. The aim was to evaluate the usefulness of our new erasing method to erase unerasable and reappearing latent images in CR. Method and Materials: Several types of photo‐stimulated luminescent (PSL) material, BaFBrI:Eu 2+ were examined for properties of causing unerasable latent images. PSL sheets were exposed to X‐ray beams of 150 kV in the range 8.07 mGy ‐ 24.2 Gy. After fully erasing with visible light, the latent images were read out by the stimulation of Eu 2+ luminescence with 633 nm He‐Ne laser light of a conventional Fuji reader. Our new method of simultaneously exposing PSL sheets with an ultraviolet light and a fluorescent light has been applied to unerasable latent images. UV lights (shorter than 270 nm) excite Eu 2+ ions, inducing strong luminescence. To avoid excitation of the Eu ion, we used ultraviolet light filtered by the UV‐29 ultraviolet transmitting optical filter, which cuts out 50% of light at 290 nm, to do the erasing. Results: Unerasable latent images were observed in all types of PSL sheets after X‐ray irradiation. After repeated treatment by the new erasing method, unerasable latent images were completely erased without reappearing PSL signals. Deep electron centers created by high X‐ray irradiation or pre‐existing centers may act as competitive trap centers to the F centers. Electrons from deep electron centers can be supplied to the F centers, causing unerasable latent images. UV lights around 290 nm can excite the deep centers relevant to the unerasable and reappearing PSL. Conclusion: The new erasing method can be used to erase unerasable and reappearing latent images effectively, reducing artifacts and improving image quality in CR.