'Detector' p6 Searchterm 'Detector' found in 1 term [ • ] and 40 definitions [• ]Result Pages : • (FOV)
The field of view is the maximum diameter of the area of the scanned object that is represented in the reconstructed image. It can also be the surface of the used detector. Further Reading: Basics: •
Filter grids are used to reduce scattered noise and increase contrast in x-ray images. Primary radiation passing through an object gets scattered caused by the various density of different materials. Scatter radiation produces noise (radiographic fog) on the film or detector, which degrades the diagnostic quality. Anti-scatter grids act as filters between patient and film (or receiver) to remove scatter radiation. The use of a grid is recommended with body parts thicker than 10 cm and kVp values about 60 kV. X-ray filter grids are available with focused or parallel strips. These two types are produced with linear or crossed grid configurations. The septa of filter grids consist of high radiation absorbing materials (e.g. lead) separated by permeable parts. During radiation exposure, movement of the grid blurs a projection of the septa. If the image receptor and x-ray tube (with the focal spot) are in a fixed position relative to one another the grid is automatically aligned. In mobile radiography, the position of the focal spot and the image receptor is variable. Additionally cassettes incorporating anti-scatter grids are also available. •
When invented, a fluoroscopic system consisted of x-ray tube, fluorescent screen and x-ray table. In 1950's, the development of the image intensifier revolutionized fluoroscopes. The basic components are extended by a gantry, image intensifier, camera, film and monitor system. The x-ray tube is usually located under the patient table, in opposition to the image intensifier and film cassette or display unit. The patient table can be rotated to an upright position for certain examinations and can be lowered to horizontal position for other imaging procedures. In some instances, the unit can be operated from outside the room. Today, the transition from conventional to digital fluoroscopy replaces the image intensifier. A flat-panel detector in combination with sensitive image sensors and digital image processing improves the diagnostic ability of a modern system. Further Reading: Basics:
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(Scintillation Camera, Scintillation Gamma Camera, Gamma Scintillation Camera or Anger Gamma Camera)
A gamma camera is an imaging device used in nuclear medicine to scan patients who have been injected, inhaled, or ingested with small amounts of radioactive materials emitting gamma rays. The gamma camera records the quantity and distribution of the radionuclide that is attracted to a specific organ or tissue of interest. The first gamma camera was developed and introduced by Hal O. Anger in 1957/58. The structure hasn't changed by today. A gamma camera consists of:
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a collimator, usually a multihole collimator;
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detector crystals, typically thallium-activated NaI scintillation crystal are used;
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photomultiplier tube array
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shielding to minimize background radiation
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position logic circuits
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and the data analysis computer
Through this design the simultaneous registration of gamma ray photons is possible, the computer further allows dynamic imaging. See also Pinhole, Elution, Center of Rotation, First Pass Scintigraphy, and Anger Hal Oscar. Further Reading: Basics:
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The gantry is a ring-shaped structure, containing the x-ray tube, collimators, filters, data acquisition system (DAS), associated electronics such as gantry angulation motors, rotational components including slip ring systems and the detector array in a CT or radiation therapy system. The table control, to regulate the gantry tilt and laser (or high intensity) lights are included within, or mounted on the gantry serving as anatomical positioning guides. To scan the patient, the patient table is moved through the gantry aperture. The rotating arm on which an accelerator head is mounted is also called gantry. This gantry can rotate 360 degrees around its axis. Result Pages : |