Computed Radiography

摘要

Computed radiography (CR) is an Image acquisition process that is used to create digital, 2-dimensional radiographs. CR employs a photostimulable phosphor-based imaging plate, replacing the Standard x-ray film and intensifying screen combination. Conventional radiographic exposure equipment is used with no modification required to the existing System. CR can transform an analog x-ray department into a digital one and eliminates the need for chemicals, water, darkrooms and film processor headaches. Discovered in 1975 by George Luckey at Eastman Kodak, the flexible storage phosphor imaging plate is similar to a Standard x-ray cassette in physical appearance. It contains a phosphor layer of fine-grain barium fluorohalide crystals doped with a divalent europium (Eu2~+). When the storage phosphor imaging plate is exposed to x-rays, electrons of the screen are excited to a higher energy level and are trapped in halide vacancies to form color centers. Holes created by the missing valence electrons cause Eu2+ to become Eu3~+.This process is non-destructive and is stable for many hours to several days.