Experimental validation of dose distributions predicted by a treatment planning system for complex models

The trend towards dose escalation in radiation therapy creates the need for non-coplanar beam arrangements to help minimize healthy tissue morbidity in the proximity of treatment volumes. Treatment planning software packages are able to generate external beam non-coplanar isodose distributions and this must be validated before use in a clinical setting. Kodak XV film was used to measure the relative dose within various tissue equivalent phantoms for comparison with the distributions predicted by the G.E. Target ("Target") treatment planning software. The results confirm that Target is able to predict the isodose distribution for coplanar and non-coplanar beams incident on patient equivalent phantoms containing relatively large, semi-infinite inhomogeneities well enough to warrant its implementation into routine clinical use. However, we have found that Target may not be able to adequately predict dose distributions around smaller inhomogeneous inclusions. Further work will be required to investigate this potential problem.