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Unsharpness
Unsharpness is the loss of spatial resolution in a Radiography, radiographic image. There are generally considered to be three types of unsharpness: geometric unsharpness, motion unsharpness and photographic or system unsharpness. Motion unsharpness is caused by movement of the patient, the detector or the source of X-rays, during the exposure. Movement of the patient, either voluntary or otherwise, is the most common cause and this can be minimised in a number of ways: immobilizing the patient, asking the patient to keep still or to hold the breath and keeping exposure time short, and thereby giving them less time in which to move, are the most obvious. System unsharpness (previously called photographic unsharpnesss) is the result of the detector system employed. Every detector type has a limiting factor which determines its maximum spatial resolution. In film systems it is the size of the grains of photographic chemical. In Photostimulated luminescence, computed radiography syst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spatial Resolution
In physics and geosciences, the term spatial resolution refers to distance between independent measurements, or the physical dimension that represents a pixel of the image. While in some instruments, like cameras and telescopes, spatial resolution is directly connected to angular resolution, other instruments, like synthetic aperture radar or a network of weather stations, produce data whose spatial sampling layout is more related to the Earth's surface, such as in remote sensing and satellite imagery. See also * Image resolution * Ground sample distance * Level of detail * Resel In image analysis, a resel (from ''res''olution ''el''ement) represents the actual spatial resolution in an image or a volumetric dataset. The number of resels in the image may be lower or equal to the number of pixel/voxels in the image. In an act ... References Accuracy and precision {{physics-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiography
Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeutic") and industrial radiography. Similar techniques are used in airport security (where "body scanners" generally use backscatter X-ray). To create an image in conventional radiography, a beam of X-rays is produced by an X-ray generator and is projected toward the object. A certain amount of the X-rays or other radiation is absorbed by the object, dependent on the object's density and structural composition. The X-rays that pass through the object are captured behind the object by a detector (either photographic film or a digital detector). The generation of flat two dimensional images by this technique is called projectional radiography. In computed tomography (CT scanning) an X-ray source and its associated detectors rotate around the su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz ( to ) and energies in the range 145 eV to 124 keV. X-ray wavelengths are shorter than those of UV rays and typically longer than those of gamma rays. In many languages, X-radiation is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it on November 8, 1895. He named it ''X-radiation'' to signify an unknown type of radiation.Novelline, Robert (1997). ''Squire's Fundamentals of Radiology''. Harvard University Press. 5th edition. . Spellings of ''X-ray(s)'' in English include the variants ''x-ray(s)'', ''xray(s)'', and ''X ray(s)''. The most familiar use of X-rays is checking for fractures (broken bones), but X-rays are also used in other ways. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photostimulated Luminescence
Photostimulated luminescence (PSL) is the release of stored energy within a phosphor by stimulation with visible light, to produce a luminescent signal. X-rays may induce such an energy storage. A plate based on this mechanism is called a photostimulable phosphor (PSP) plate and is one type of X-ray detector used in projectional radiography. Creating an image requires illuminating the plate twice: the first exposure, to the radiation of interest, "writes" the image, and a later, second illumination (typically by a visible-wavelength laser) "reads" the image. The device to read such a plate is known as a phosphorimager (occasionally spelled phosphoimager, perhaps reflecting its common application in molecular biology for detecting radiolabeled phosphorylated proteins and nucleic acids). Projectional radiography using a photostimulable phosphor plate as an X-ray detector can be called "phosphor plate radiography" or "computed radiography" (not to be confused with computed tomography ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital Radiography
Digital radiography is a form of radiography that uses x-ray–sensitive plates to directly capture data during the patient examination, immediately transferring it to a computer system without the use of an intermediate cassette. Advantages include time efficiency through bypassing chemical processing and the ability to digitally transfer and enhance images. Also, less radiation can be used to produce an image of similar contrast to conventional radiography. Instead of X-ray film, digital radiography uses a digital image capture device. This gives advantages of immediate image preview and availability; elimination of costly film processing steps; a wider dynamic range, which makes it more forgiving for over- and under-exposure; as well as the ability to apply special image processing techniques that enhance overall display quality of the image. Detectors Flat panel detectors 250px, Flat panel detector used in digital radiography Flat panel detectors (FPDs) are the most common ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thin Film Transistors
A thin-film transistor (TFT) is a special type of field-effect transistor (FET) where the transistor is thin relative to the plane of the device. TFTs are grown on a supporting (but non-conducting) substrate. A common substrate is glass, because the traditional application of TFTs is in liquid-crystal displays (LCDs). This differs from the conventional bulk metal oxide field effect transistor ( MOSFET), where the semiconductor material typically ''is'' the substrate, such as a silicon wafer. Design and Manufacture TFTs can be fabricated with a wide variety of semiconductor materials. Because it is naturally abundant and well understood, amorphous or polycrystalline silicon was historically used as the semiconductor layer. However, because of the low mobility of amorphous silicon and the large device-to-device variations found in polycrystalline silicon, other materials have been studied for use in TFTs. These include cadmium selenide, metal oxides such as indium gallium zi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
