Ct Scanner: From 1 Different Sources
The machine which combines the use of a computer and X-rays to produce cross-sectional images of the body (see COMPUTED TOMOGRAPHY).
A technique by which temperature patterns on the surface of the skin are recorded in the form of an image. Thermography provides clues to the presence of diseases and abnormalities that alter the temperature of the skin, such as problems of the circulation, inflammation, and tumours. There are 2 types of thermography. In one, a camera or scanner picks up infrared radiation naturally emitted from the skin. In the other, sheets of temperature-sensitive liquid crystals are applied to the skin; they change colour in response to changes in temperature.... thermography
n. a sequential set of instructions used in calculations or problem solving. A reconstruction algorithm is a complex mathematical formula used by a computer to construct images from the data acquired by CT, MRI, or other scanners. A diagnostic algorithm or a therapeutic algorithm consists of a stepwise series of instructions with branching pathways to be followed to assist a physician in coming to a diagnosis or deciding on a management strategy, respectively.... algorithm
(single photon emission computing tomography) (in nuclear medicine) a *cross-sectional imaging technique for observing an organ or part of the body using a *gamma camera; images are produced after injecting a radioactive *tracer. The camera is rotated around the patient being scanned. Using a computer reconstruction *algorithm similar to that of a *computerized tomography scanner, multiple ‘slices’ are made through the area of interest. SPECT scanning is used particularly in cardiac nuclear medicine imaging (see MUGA scan). It differs from PET scanning in that radioactive decay gives off only a single gamma ray.... spect scanning
(helical CT scanning) a development of conventional *computerized tomography (CT) scanning in which the X-ray tube rotates continuously around the patient as he or she passes through the scanner. This allows the acquisition of images throughout a specified volume of tissue much more quickly. Since these images are digitally acquired (see digitization), *post-processing can produce images in numerous planes, without further exposure of the patient to ionizing radiation. See also multidetector computerized tomography.... spiral ct scanning
n. the *SI unit of magnetic flux density, equal to a density of 1 weber per square metre. This unit is important in *magnetic resonance imaging (MRI). Most MRI scanners operate between 0.1 and 2.5 T, but some modern research scanners may go up to 7 T. Symbol: T.... tesla
n. imaging of blood vessels (see also coronary angiography; lymphangiography). In the older form of angiography X-ray imaging was carried out after injection of *radiopaque contrast medium and *digital subtraction applied to enhance visualization. The use of X-rays has now been largely replaced by methods using MRI or CT scanners. Magnetic resonance angiography (MRA) can be performed with (contrast-enhanced) or without (noncontrast) injection of a magnetic resonance contrast agent (see contrast medium). Contrast-enhanced MRA will show the vessels better. These images can be reconstructed in two or three dimensions. Computerized tomographic angiography (CTA) uses a radiographic contrast agent, usually injected into a vein, to increase the visibility of the blood vessels. Fluorescein angiography is a common method of investigation in ophthalmology. *Fluorescein sodium is injected into a vein in the arm, from which it circulates throughout the body. Light of an appropriate wavelength is shone into the eye, causing the dye in the retinal blood vessels to fluoresce. This allows the circulation through the retinal blood vessels to be observed and photographed. Indocyanine green (ICG) angiography uses indocyanine green dye, which fluoresces in infrared light. It is valuable in assessing circulation in the deeper layers of the *fundus.... angiography
(CT) a form of X-ray examination in which the X-ray source and detector (CT scanner) rotate around the object to be scanned and the information obtained can be used to produce cross-sectional images (see cross-sectional imaging) by computer (a CT scan). A higher radiation dose is received by the patient than with some conventional X-ray techniques, but the diagnostic information obtained is far greater and should outweigh the increased risk. CT scanning can be used for all parts of the body. The data obtained can be used to construct three-dimensional images of structures of interest. See also multidetector computerized tomography; spiral CT scanning.... computerized tomography
(MDCT) a development of *spiral CT scanning that uses more than one array of detectors opposite the X-ray tube, so that more tissue can be included, with thinner cuts, in a single rotation of the machine. This is particularly important for three-dimensional reconstruction of tissues. It also allows volumetric scanning or *isotropic imaging, which are best achieved when the thickness of the slice is similar to the size resolution of the detectors in the other two planes. Modern CT scanners are now usually equipped with between 16 and 640 detector arrays. The technique is particularly valuable for imaging fast-moving structures, such as the heart.... multidetector computerized tomography
(PET) a technique in nuclear medicine for *cross-sectional imaging that enables a noninvasive assessment and localization of metabolic activity to be made. Originally used to study activity in the brain, PET is now also used for investigating the chest and abdomen. Emission of a *positron by a radioisotope results in annihilation of the positron on collision with an electron, and the creation of two gamma rays of known energy travelling in exactly opposite directions. The PET scanner has detectors on each side of the patient to detect the simultaneous arrival of the gamma rays. Images are created using reconstruction *algorithms similar to CT scanning. *Fluorodeoxyglucose, labelled with fluorine-18, is used to examine glucose metabolism, and ammonia, labelled with nitrogen-13, gives information on perfusion. Carbon-11 and oxygen-15 can also be used as radioisotopes for PET scanning. Some diseases result in decreased uptake of the radio-labelled material due to decreased function; others show increased glucose metabolism and concentrate the isotope avidly. In this way functional activity of the tissues can be compared with anatomical images obtained by CT or MRI scanning (see PET/CT scanning). Localized areas of increased glucose uptake revealed by PET scans can sometimes signify functional activity of malignant cells, which use more glucose than normal cells, although other processes, such as infection, can produce similar scans. PET scans can help to localize metastatic disease (see metastasis) that is not identified by other scanning techniques. See also tomography. Compare computerized tomography.... positron emission tomography
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