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Searchterm 'Screen' found in 2 terms [
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Breast Imaging
Breast imaging methods include mammography (mammogram), ultrasound, breast MRI, positron emission tomography, xeromammography, diaphanography and thermography.
Mammography is widely used as a screening method and diagnostic tool for breast cancer detection or evaluation of breast disease. Digital mammography takes multiple thin digital image 'slices' through the breast, which provides higher potential to see a small mass within dense tissue. The mammography quality standards act guarantees a high image quality.
Breast ultrasound (also called ultrasonography) should only be used as an additional imaging modality to evaluate specific breast abnormalities, especially to differentiate cystic from solid masses. Ultrasound is also used to guide needle breast biopsies.
Magnetic resonance imaging (MRI) is useful for breast MRI screening in cases of high cancer risk. In addition, multifocal breast cancer can be missed by standard practice mammography and can be early detected with breast MRI.
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Cinefluorography
A cinefluorography produces a movie (cine) film from an image intensifier during x-rays examinations (often called videofluorography, cineradiography or cine). Cinefluorography is always monitored on the TV screen normally used for fluoroscopy. The image from the output screen of the image intensifier is split with a semi-transparent mirror into two output ports; one leading to the movie camera and the other to the fluoroscopy camera. Most of the light is directed to the cine camera. The image on the monitor does not suffer in quality due to the fact that the tube current for cinefluorography is about 100 times higher than for common fluoroscopy.
The x-ray generator pulses are synchronized with the movements of the cine camera, so that no x-rays are emitted when the film is moved forward to the next frame. The needed very accurate synchronization of the x-ray generator can be achieved by use of high voltage switching in the secondary circuit of the constant potential x-ray generator, by starting and stopping the inverter in a medium frequency generator or by using a grid controlled x-ray tube.
Conventional Radiography
Conventional (also called analog, plain-film or projectional) radiography is a fundamental diagnostic imaging tool in the detection and diagnosis of diseases. X-rays reveal differences in tissue structures using attenuation or absorption of x-ray photons by materials with high density (like calcium-rich bones).
Basically, a projection or conventional radiograph shows differences between bones, air and sometimes fat, which makes it particularly useful to asses bone conditions and chest pathologies. Low natural contrast between adjacent structures of similar radiographic density requires the use of contrast media to enhance the contrast.
In conventional radiography, the patient is placed between an x-ray tube and a film or detector, sensitive for x-rays. The choice of film and intensifying screen (which indirectly exposes the film) influence the contrast resolution and spatial resolution. Chemicals are needed to process the film and are often the source of errors and retakes. The result is a fixed image that is difficult to manipulate after radiation exposure. The images may be also visualized on fluoroscopic screens, movies or computer monitors.
X-rays emerge as a diverging conical beam from the focal spot of the x-ray tube. For this reason, the radiographic projection produces a variable degree of distortion. This effect decreases with increased source to object distance relative to the object to film distance, and by using a collimator, which let through parallel x-rays only.
Conventional radiography has the disadvantage of a lower contrast resolution. Compared with computed tomography (CT) and magnetic resonance imaging (MRI), it has the advantage of a higher spatial resolution, is inexpensive, easy to use, and widely available. Conventional radiography can give high quality results if the technique selected is proper and adequate. X-ray systems and radioactive isotopes such as Iridium-192 and Cobalt-60 for generating penetrating radiation, are also used in non-destructive testing.

See also Computed Radiography and Digital Radiography.
Fluoroscope
A fluoroscope projects x-ray images in a video sequence (movie) onto a screen monitor.
Early generation fluoroscopes presented particularly difficult viewing challenges for radiologists. The human retina contains two types of image receptors. Cones (central vision) operate better in bright light, while rods (peripheral vision) are more sensitive to blue-green light and low light. Therefore, the radiologists wear red goggles to filter out blue-green wavelengths to allow the rods to recover peak sensitivity before viewing fluoroscopic images.
To avoid this time consuming accommodation, the industry developed the image intensifier tube in the 1950s. Due to the high amount of individual images during a fluoroscan, a very sensitive amplifier is needed to cut down radiation exposure. Until today, image intensifiers amplify the faint light emitted by the fluorescing screen and the images can be viewed on a monitor. Recently, digital technique replaces the large and bulky image intensifier with flat-panel technology.
Various other components of a fluoroscope system include a gantry, patient table, x-ray tube, filters, collimators, images sensor, camera and computer, most similar to other radiographic systems.
A fluoroscopy system provides the view of moving anatomic structures and is valuable in performing procedures that require continuous imaging and monitoring, such as barium studies, gastrointestinal function tests, cardiac functions, studies of diaphragmatic movement, or catheter placements. A number of technologies are available to record images created during fluoroscopic (fluorographic) exams.
Intrinsic Conversion Efficiency
The intrinsic conversion efficiency is the efficacy of an intensifying screen in converting x-rays into light photons.
For example, the radiation to light conversion efficiency of calcium tungstate is less than the efficiency of rare earth screens (about 5% vs. 12 - 18%).
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