Physichal parameters for wedge filters used in radiotherapy

Wedge filters using in radiotherapy up two important problems: attenuation of gamma rays introduced by the presence of wedge filters and spinning of isodoses curves plate. Depending of irradiation geometry, characterised by Dw, - source filter distance, Dc - source dose's estimate point distance, a - side of irradiation field; nature and size filter: α - wedge angle, μ - linear adsorption coefficient, ε - filter cover attenuation w - filter side, and nature of target volume characterised by μ' - linear absorption coefficient of medium has been estimated absorption factor of wedge filter (kw) for two irradiation geometry: and spinning angle of isodose plate (Θ): 3) tg θ (μDw(μ'Dc - 2 Calculated values has been compared with the experimental measured values, for a cobaltotherapy unit Rokus-M, and the result was that between the two series of dates it is a good concordance