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Searchterm 'X-Ray' found in 8 terms [
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Dynamic Range
The dynamic range describes the range of x-ray intensities a detector can differentiate. A high dynamic range provides the discrimination between small differences in x-ray attenuation.
A current CT scanner has approximately a dynamic range of 1,000,000 to 1 and 1,100 views or projections a second.
Effective Energy
The effective energy (related to bremsstrahlung radiation from an x-ray machine) is the monoenergetic photon energy which produces the same first half value layer in a given material as the x-ray beam.
Filament
The filament is the source of electrons (cathode) in x-ray tubes. A thin wire (0.1- 0.5 mm, usually tungsten) emits electrons due to thermionic emission, operating in a vacuum and energized with electric current.
A CT tube utilizes a larger filament with larger size of the effective focal spot than a conventional x-ray tube.
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.
Grid
Grids are used in a test phantom to check the quality of x-ray images. Such a grid may consist for example, of gold structures on a silicon surface and a grid period length of 2 micrometer with space wide in between of 1 micrometer.
Filter grids are also used in x-ray imaging to reduce noise contributed by scatter.
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 [last update: 2023-11-06 02:01:00]