3-D treatment planning. 140

The edge model described here includes a fully three-dimensional treatment of field shape and scatter effects, is fast, and correctly accounts for all beam divergence and other geometry. Three functions, none a function of field size, are used: a flattening filter function, the basic depth dose dependence of the infinitely-broad beam, and an 'edge' function which describes the dose as a function of the distance from the edges of the beam. This edge function is integrated around all edges of the beam in order to incorporate beam size and shape considerations. The model reproduces the equivalent square table and is useful for arbitrarily-shaped fields like those from multileaf collimators. 4 refs.; 2 figs.; 2 tabs