Abstract
Radiotherapy treatments are becoming more complex, often requiring the dose tobe calculated in three dimensions and sometimes involving the application ofnon-coplanar beams. The ability of treatment planning systems to accuratelycalculate dose under a range of these and other irradiation conditionsrequires evaluation. Practical assessment of such arrangements can beproblematical, especially when a heterogeneous medium is used. This workdescribes the use of Monte Carlo computation as a benchmarking tool to assessthe dose distribution of external photon beam plans obtained in a simpleheterogeneous phantom by several commercially available 3D and 2D treatmentplanning system algorithms. For comparison, practical measurements wereundertaken using film dosimetry. The dose distributions were calculated for avariety of irradiation conditions designed to show the effects of surfaceobliquity, inhomogeneities and missing tissue above tangential beams. Theresults show maximum dose differences of 47% between some planning algorithmsand film at a point 1 mm below a tangentially irradiated surface. Overall, thedose distribution obtained from film was most faithfully reproduced by theMonte Carlo N-Particle results illustrating the potential of MonteCarlo computation in evaluating treatment planning system algorithms.
Published Version
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