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A 1951 USAF resolution test chart is a microscopic optical resolution test device originally defined by the U.S. Air Force MIL-STD-150A standard of 1951. The design provides numerous small target shapes exhibiting a stepped assortment of precise spatial frequency specimens.
Recognized effects of higher acute radiation doses are described in more detail in the article on radiation poisoning.Although the International System of Units (SI) defines the sievert (Sv) as the unit of radiation dose equivalent, chronic radiation levels and standards are still often given in units of millirems (mrem), where 1 mrem equals 1/1,000 of a rem and 1 rem equals 0.01 Sv.
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A PACS consists of four major components: The imaging modalities such as X-ray plain film (PF), computed tomography (CT) and magnetic resonance imaging (MRI), a secured network for the transmission of patient information, workstations for interpreting and reviewing images, and archives for the storage and retrieval of images and reports.
A list of experimentally found and theoretically calculated X-ray transition energies is available at NIST. [8] Nowadays, theoretical energies are computed with much greater accuracy than Moseley's law allows, using modern computational models such as the Dirac–Fock method (the Hartree–Fock method with the relativistic effects accounted for).
Characteristic X-rays are emitted when outer-shell electrons fill a vacancy in the inner shell of an atom, releasing X-rays in a pattern that is "characteristic" to each element. Characteristic X-rays were discovered by Charles Glover Barkla in 1909, [ 1 ] who later won the Nobel Prize in Physics for his discovery in 1917.
Most X-rays occur during the third trimester of pregnancy. [8] There is sparse information on radiation exposure from the first trimester of pregnancy. [8] However, data suggests that the relative risk is 2.7. [8] Relative risk is a measure of probability of an outcome in one group versus the other.
Caldwell's view (or Occipitofrontal view) is a radiographic view of the skull where the X-ray plate is perpendicular to the orbitomeatal line. The rays pass from behind the head and are angled at 15-20° to the radiographic plate. It is commonly used to get better view of the ethmoid and frontal sinuses. [1]