Tomographic methods

Tomography - a method of not destroying level-by-level research of internal structure of object by means of its repeated show through in various crossed directions.

Tomography - a method of radiological research by means of which it is possible to make a picture of the layer lying on certain depth of investigated object. Reception of a level-by-level picture is based on moving of two of three components (an x-ray tube, an x-ray film, object of research). Method at which the investigated object is motionless, and the x-ray tube and the cartridge with a film in coordination move in opposite directions were received wide distribution.

At synchronous movement of a tube and the cartridge only the necessary layer turns out precise on a film because only its contribution to the general shadow remains motionless concerning a film, all rest - is greased, almost not preventing to spend the analysis of the received image. Now the share of last method in researches promptly decreases, it gives not enough information and bears high beam loading to the patient. The given method has received the name a classical tomography or a linear tomography.

The main difference of methods of echosounding from a tomography consists that at echosounding are visualized borders and not areas (usually parameter of refraction)

Calculable tomography - area of mathematics which develops mathematical methods and algorithms of restoration of internal structure of object on projective data.

Computer tomography - a synonym of the term a tomography (all modern tomographic methods are realized by means of computer technics); the synonym of the term a x-ray computer tomography, this method has begun a modern tomography.

The anatomic tomography - is based on reception of cuts of tissues of the person with their subsequent fixing by means of chemical substances and their registration on a photofilm. Classical examples of an anatomic tomography are images of histologic preparations. Terminologically, now, the given methods do not carry to a tomography, by virtue of their destroying character.

Classification of kinds of a tomography.

Interposition of a source of probing radiation, bject and the detector.

From the point of view of interposition of a source of probing radiation, object and the detector tomographic methods can be divided into following groups:

Transmission - the probing external radiation which has been last through passive (not radiating) object is registered, being partially weakened thus;

Issue - the radiation leaving active (radiating) object with some spatial distribution of sources of radiation is registered;

Combined transmission-issue (luminescent, acoustic and optical) - secondary radiation from the sources distributed on volume of object and raised by external radiation is registered;

Echosounding - the probing external radiation reflected from internal structures of passive object is registered.

The sizes of investigated objects:

Microlevel (microtomography) - objects with size as separate cell are investigated

Level of objects, commensurable with a human body (from separate body or the laboratory mouse till the airplane)

Macrolevel - the atmospheric phenomena (clouds, cyclones, a tornado), planets and stars.

It is possible allocate by sphere of application:

Medical tomography (as a kind of medical visualization and medical diagnostics);

Industrial (technical) tomography (as a kind defectoscopy);

Tomography of macroobjects.

Probing radiation.

Tomography with use of sound waves (including seismic):

Ultrasonic tomography;

Seismic tomography

Tomography with use of electromagnetic radiation:

Issue tomography (scale-radiation);

One-photon issue tomography

Two-photon issue tomography

X-ray tomography; X-ray computer tomography

Optical (laser) tomography

Tomography in a radio range.

Tomography with use of electromagnetic fields:

magnetic-resonant tomography (MR-tomography)

Electro-impedance tomography.

Tomography with use of elementary particles:

Neutron tomography

Electronic tomography;

Proton tomography.

For tomographic methods the similar hierarchy can be presented as:

Two-dimensional tomography: it is a lot of foreshortenings from one plane - a set of one-dimensional projections plus mathematical processing - the 2D-tomogram

Three-dimensional level-by-level tomography: it is a lot of foreshortenings in set of parallel planes - a set of one-dimensional projections plus mathematical processing - a set of 2D-tomograms - the 3D-tomogram

Three-dimensional any tomography: it is a lot of foreshortenings in set of crossed planes - a set of one-dimensional projections plus mathematical processing - the 3D-tomogram

We receive distribution of some physical characteristic (areas of points of easing are restored). One foreshortening gives not enough information, therefore there is a necessity in repeated просвечивании in various crossed directions.