Dosimetric verification of radiotherapy treatment planning system (TPS) represents an important step in the commissioning process. The accuracy of a calculated dose distribution is one of the most important requirements for a good commercial treatment planning system. Verification of the TPS accuracy may be performed in two different ways – by comparing calculated and measured data for given geometries and test points or by utilising a standard set of test data. Results of dosimetric verification of the CadPlan treatment planning systemusingAAPMReport No. 55 data are presented in this paper. In the case of homogenous phantom the average deviation was 0.8 % and we got a pass result for tolerance 2% in 98% of the test points, average deviation in the heterogenous phantom was 1% and the pass rate for tolerance 3% was 100%. Results of the dosimetric verification show that CadPlan meets commonly accepted criteria for a clinical use.

        Key words: radiotherapy treatment planning system – quality assuarance