A simple computational approach to irregular field dosimetry

Treatment of certain malignant tumors requires very large and irregular fields. The dose computations in such field configurations are quite complicated and tedious and hence accessible to computer methods only. This paper describes an easy method for estimating dose to any point in such irregular fields except those which are in the shielded region. For radiotherapy centres which do not have access to a computer, this paper presents an algorithm that can be used with a desk calculator for dose computation at any point. The dose values calculated using this algorithm at different points and at different depths in the mantle and inverted Y-fields agree within +/- 3% with the values computed using detailed sector integration method of Clarkson.