POLE of RADIATION in radiology

From Big Medical Encyclopedia

The FIELD of RADIATION in radiology — section of a bunch of the ionizing radiation created by the collimator (diaphragm) of the device for remote radiation therapy (a X-ray apparatus, the gamma device, a particle accelerator) on a surface or various depth of the irradiated body.

Distinguish geometrical and physical P. of the lake. Geometrical P. of the lake is defined by a projection of bottom edge of the diaphragm constructed of the center of an end face of a source in cross-section of a bunch of ionizing radiation. Physical P.'s borders of the lake are defined on chosen for these conditions of radiation to an isodose (see). In radiation therapy the lakes created by means of the special blocks installed within the geometrical field of radiation — so-called figured P. of the lake use P.

On P.'s border of the lake there is an area of a half-shade caused by the sizes of a source of ionizing radiation, geometry of its bunch, partial absorption of ionizing radiation in the collimator and also its dispersion in the irradiated body and in structural elements of the device. So, in the gamma and therapeutic device the source of ionizing radiation is not dot that leads to formation considerably of a bigger half-shade, than in the dynamitrons having almost point source of radiation. In a wedge, the practician P. of the lake on the surface of the irradiated body control by means of the light bunch modeling a bunch of ionizing radiation.

See also Collimation .

Bibliography: Ratner T. G. and Bibergal A. V. Formation of dozny fields at a remote gamma therapy, M., 1972.

M. A. Fadeyeva.