Visible light can be seen by the naked eye (and thus forms images that people can look at), but it does not penetrate most objects (only translucent ones). In contrast, X-rays can penetrate a wider variety of objects (such as the human body), but they are invisible to the naked eye. To take advantage of the penetration for image-forming purposes, one must somehow convert the X-rays' intensity variations (which correspond to material contrast and thus image contrast) into a form that is visible. Classic film-based radiography achieves this by the variable chemical changes that the X-rays induce in the film, and classic<unk>  achieves it by<unk> scence, in which certain materials convert X-ray energy (or other parts of the spectrum) into visible light. This use of<unk> scent materials to make a viewing scope is how<unk>  got its name. As the X-rays pass through the patient, they are attenuated by varying amounts as they pass through or reflect off the different tissues of the body, casting an X-ray shadow of the radiopaque tissues (such as bone tissue) on the<unk> scent screen. Images on the screen are produced as the unattenuated or mildly attenuated X-rays from radiolucent tissues interact with atoms in the screen through the photoelectric effect, giving their energy to the electrons. 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<unk> c images by sitting in darkened rooms, or by wearing red adaptation goggles. After the development of X-ray image intensifiers, the images were bright enough to see without goggles under normal ambient light. Nowadays, in all forms of digital X-ray imaging (radiography,<unk> , 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 detectors, which convert the X-ray energy into electrical signals, small bursts of current that convey information that a computer can analyze, store, and output as images. As<unk> scence is a special case of luminescence, digital X-ray imaging is conceptually similar to digital gamma ray imaging (scintigraphy, SPECT, and 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 processed by a computer and made output as a visible-light image.
Fluoroscopy
Frozen pelvis
Radiography
Scintigraphy
Palpation
Exploratory surgery
Contrast CT
Volume CT