EMISSION COMPUTER TOMOGRAPHY

From Big Medical Encyclopedia

EMISSION COMPUTER TOMOGRAPHY — the method of a ra-dioizotopny research based on registration of radiation of the radionuclide entered into an organism and the subsequent creation of layer-by-layer images by means of the COMPUTER.

It is offered by the Sack (D. E. Kuhl) in 1963. It designed the first issue computer tomograph. Depending on a research objective and the used ra-diofarmatsevtichesky drugs distinguish two look E. to. t. — one-photon and positron.

One photon emission computer tomography is applied at diagnosis of volume educations and vascular disorders of a brain; disturbances of blood circulation of a myocardium at coronary heart disease; in pulmonology, especially for the purpose of early detection of a thrombembolia of pulmonary arteries. This look E. k.t. it is perspective for diagnosis of diseases of a liver, kidneys, detection of metastasises of a tumor in bones. The method allows to obtain by the analysis of a series of layer-by-layer cuts the objective information about an anato-mo-topographical and functional condition of body, and also to define prevalence patol. process.

For carrying out one-photon E. to. t. use the gamma matsevtichesky drugs radiating radio headlights (see). The research is conducted by means of gamma cameras with the special collimating devices for obtaining scintigraphic images of bodies under certain corners or method of a multiprojective stsintigrafiya by means of so-called rotational gamma cameras. At rotation of the detector of the gamma camera around the patient receive from 32 to 128 scintigraphic projections for a whole revolution, to-rye form a basis for creation of tomographic images. At a research of various bodies choose certain conditions of laying of the patient and the physics and technology modes of a research. The patient is stacked so that the center of a trajectory of rotation of the detector of the gamma camera corresponded to the studied body. Because cross section of a body of the person can be conditionally presented as an ellipse, designs of nek-ry tomographs provide rotation of the sensor on an ellipsoidal curve.

At one-photon E. to. t. a brain, lungs, a liver, kidneys, a skeleton use the mode with a whole revolution of the detector of the gamma camera around a longitudinal axis of a body of the person. Optional versions with repeated rotation of the detector, and also with fragmentary record when the registering system joins only during the passing of the sensor in the Set sectors. At reconstruction of tomographic cuts their total number and thickness are chosen depending on an objective; the minimum thickness of a cut fluctuates from 5 to 10 mm. Cuts receive in axial, sagittal, frontal and slanting projections.

The positron emission computer tomography is carried out with use of special group of the radio-pharmaceuticals containing ultrashort-lived pozitronizluchayushchy isotopes of oxygen, nitrogen, iron, to-rye are included natural metabolites, napr, glucose, amino acids, etc. It gives the chance, in addition to obtaining tomographic images, to study metabolism of bodies and systems, napr, metabolism and a condition of microcirculation of a myocardium. The perspective direction is definition by means of positron E. to. t. focal defeats and regional vascular changes at patients with epilepsy. Positron E. to. t. — the only noninvasive method allowing to estimate quantitatively regional cerebral metabolism and a blood stream, opredzlyat a zone of chronic ischemia, boundary with a heart attack.

For carrying out positron E. to. t. use mnogodatchikovy systems (issue computer tomographs), in to-rykh radiation is registered by means of a large number of the scintillation detectors located around the studied object. Summary information comes from each sensor to the computer, in Krom according to special programs the tomographic cut forms. Distinctiveness of the issue computer tomographs used for positron E. to. t., simultaneous registration of couples of multidirectional photons is.

Due to short half-lives of positron radionuclides carrying out positron E. to. t. perhaps only in the large diagnostic centers located in close proximity to the cyclotron generating these isotopes.

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