Physicotechnical bases of a roentgenology

Roentgenologic diagnostics, computer tomography, spiral computer tomography, magnetic-resonance imaging, diagnostic ultrasound, termography

Radiological method of evaluation

For the reception of the radiological image of internal organs a fascicle of an electromagnetic X-ray radiation is passed through the body of the patient. According to the law of physics as a result of non-uniform absorption and dispersion of a part of quantums which is caused by non-uniform density of the tissues, this fascicle is un-uniformly weakened. Getting out from the body of the person the fascicle of a X-ray radiation carries the image of the structure which is studied.

Physicotechnical bases of a roentgenology

Generator of X-ray radiation is the X-ray tube – it is a bi-electrode electrovacuum device intended for the reception, acceleration and inhibition of electrons gathering around the string of the cathode as a result of thermionic emission. By leading high current to the electrodes of the tube, there is an acceleration and prompt movement to the anode of the electrons focused on the cathode of the electromagnetic floor. The tube is generated with the electric current. Considerably the most part of the kinetic energy of electrons in the substance of an anode turns into thermal energy and only nearby 1 % - in a X-ray radiation. The scheme of a X-ray tube is shown in fig.10.1.

Fig. 10.1 The scheme of an X-ray tube

1 - glass cylinder; 2 - rotor; 3 - disk of the anode; 4 - focal maculae of anode; 5 - focal system of spiral of the cathode; 6 - stream of electrons; 7 - stream of X-ray quantums

The X-ray radiation passes through opaque optic mediums and cooperates with substance and as a result there is a non-uniform absorption.

Photochemical influence of X-ray radiation underlies on the reception of the x-ray image on the film where the gelatinous layer of the film contains crystals galloid silver in the form of an emulsion.Property of an X-ray radiation to cause fluorescence is a basis of a roentgenoscopy and use of X-ray intensifying screens during roentgenography.

The X-ray diagnostic apparatus consists of device which generates X-ray radiation (radiant - X-ray tube and the feeding device), supporting mechanical device, the receiver of radiation, the devices forming the x-ray image and a control panel. The basic scheme of the device of a X-ray apparatus is shown in fig. 10.2.

Fig. 10.2 The basic chart of the device of an X-ray apparatus

1 -electric system; 2 - the transformer; 3 - system of rectifiers; 4 - X-ray tube; 5 - control panel; 6 - power unit; 7 - support.

Receivers of radiation serve the visualization of an X-ray radiation which has passed through investigating object and carry the latent image. For the visualization of the image special fluorescent screens are used, cartridges with x-ray film, detectors of radiation with EOA (electron-optical amplifier) and digital systems of visualization of the image.

On the screen, on film (after its photo processing) or on the screen of the COMPUTER there is a visible x-ray image of the object. The X-ray image represents the model of the object which gives authentic representation about its structure, the form and functions of the organs and systems of the person.

Apratus for the general radiodiagnosis is used with a universal rotary table-support for the lumination and for carrying out the roentgenography in vertical and horizontal positions of the patient. The table for roentgenography is equipped with the device for carrying out longitudinal tomography in horizontal position of the patient.

In pediatric roentgenology use of the special tables-support is intended for carrying out the multipositional inspection of the children of different age groups, similarly separate specialized workplaces for two-or three-axial mutipositional investigation. hinged devices of the apparatus is a general purpose.

Дата добавления: 2015-10-23