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This makes CT scan the most appropriate term, which is used by radiologists in common vernacular as well as in textbooks and scientific papers. [218] [219] [220] In Medical Subject Headings (MeSH), computed axial tomography was used from 1977 to 1979, but the current indexing explicitly includes X-ray in the title. [221]
In conventional CT machines, an X-ray tube and detector are physically rotated behind a circular shroud (see the image above right). An alternative, short lived design, known as electron beam tomography (EBT), used electromagnetic deflection of an electron beam within a very large conical X-ray tube and a stationary array of detectors to achieve very high temporal resolution, for imaging of ...
Fig.1: Basic principle of tomography: superposition free tomographic cross sections S 1 and S 2 compared with the (not tomographic) projected image P Median plane sagittal tomography of the head by magnetic resonance imaging. Tomography is imaging by sections or sectioning that uses any kind of penetrating wave.
CT is based on the same principles as X-ray projections but in this case, the patient is enclosed in a surrounding ring of detectors assigned with 500–1000 scintillation detectors [13] (fourth-generation X-ray CT scanner geometry). Previously in older generation scanners, the X-ray beam was paired by a translating source and detector.
Though CT uses a higher amount of ionizing x-radiation than diagnostic x-rays (both utilising X-ray radiation), with advances in technology, levels of CT radiation dose and scan times have reduced. [9] CT exams are generally short, most lasting only as long as a breath-hold, Contrast agents are also often used, depending on the tissues needing ...
The original 1971 prototype took 160 parallel readings through 180 angles, each 1° apart, with each scan taking a little over 5 minutes. The images from these scans took 2.5 hours to be processed by algebraic reconstruction techniques on a large computer. The scanner employed a pencil X-ray beam aimed at a single photomultiplier detector, and ...
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Such scans are most useful for tissues outside the brain, where location of tissues may be far more variable. For example, SPECT/CT may be used in sestamibi parathyroid scan applications, where the technique is useful in locating ectopic parathyroid adenomas which may not be in their usual locations in the thyroid gland.