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As the X-rays pass through the patient, they are [[attenuation|attenuated]] by varying amounts as they [[refraction|pass through]] or [[reflection (physics)|reflect off]] the different [[tissue (biology)|tissues]] of the body, casting an X-ray [[shadow]] of the [[radiodensity|radiopaque]] tissues (such as [[bone tissue]]) on the fluorescent screen. Images on the screen are produced as the unattenuated or mildly attenuated X-rays from [[radiodensity|radiolucent]] tissues interact with atoms in the screen through the [[photoelectric effect]], giving their energy to the [[electron]]s. While much of the energy given to the electrons is dissipated as [[heat]], a fraction of it is given off as visible light.
Early radiologists would adapt their eyes to view the dim fluoroscopic images by sitting in darkened rooms, or by wearing [[red adaptation goggles]]. After the development of [[X-ray image intensifier]]s, the images were [[brightness|bright]] enough to see without goggles under normal [[available light|ambient light]].<ref>{{Cite web |title=Red Goggles (ca. 1940s) |url=https://www.orau.gov/health-physics-museum/collection/radiology/fluoroscopy/red-goggles.html |access-date=2022-03-23 |website=Museum of Radiation and Radioactivity |language=en}}</ref> Image Intensifiers are still being used to this day (2023) with many new models still using II (Image Intensifier) as its method of acquiring the image which is still popular due to lower cost compare to Flat
Nowadays, in all forms of digital X-ray imaging (radiography, fluoroscopy, and CT) the conversion of X-ray energy into visible light can be achieved by the same types of electronic sensors, such as [[flat panel detector]]s, which convert the X-ray energy into electrical [[signal (electrical engineering)|signals]]: small bursts of [[electric current]] that convey information that a computer can analyze, store, and output as images. As fluorescence is a special case of [[luminescence]], digital X-ray imaging is conceptually similar to digital [[gamma ray]] imaging ([[scintigraphy]], [[single-photon emission computed tomography|SPECT]], and [[positron emission tomography|PET]]) in that in both of these imaging mode families, the information conveyed by the variable attenuation of invisible electromagnetic radiation as it passes through tissues with various radiodensities is converted by an electronic sensor into an electric signal that is [[signal processing|processed by a computer]] and output as a visible-light image.
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