Electron irradiation field dose equaliser for radiotherapy - has absorbing screen in electron beam path between radiation source and treatment field

摘要

The device equalises the radiation dose in an electron irradiation field, determined by a beam of electrons (2) at a distance (D1) from a source (3) contained in an irradiation equipment (40). The source generates the beam in a reference direction (A). The device consists of a screen (16) for absorbing electrons which is situated between the radiation field (12) and the source at a distance (D2) from the source. The screen is made of stainless steel and its position is adjustable along the reference direction between the irradiation equipment and the irradiation field. The diameter of the screen (d1) is less than the diameter (d2) presented by the cross-section of the beam at the point where the screen is situated. The screen occupies the central part of the beam. The electrons scattered in air over a distance D3 between the screen and the radiation field then produce a homogeneous irradiation dose over the field.