• Progress in Medical Physics
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• v.15 no.2
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• pp.77-83
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• 2004

The commissioning of a model-based treatment planning system requires many parameters to fit the measured depth doses and transverse profiles. For the commissioning of the Pinnacle$^3$ system, through the Monte Carlo (MC) simulation, the necessary parameters, including the photon spectrum, contaminant electrons, off-axis softening and fluency of photons, were observed. Through the simulation the parameters contained valuable information, but the calculated results of the Pinnacle$^3$ using the MC-derived parameters showed discrepancies with those measured for the off-axis softening and the fluency of photons. Even though the MC calculation produces reasonable values for the commissioning, the thorough physical basis of the Pinnacle$^3$'s commissioning process is needed in order to directly use the MC derived parameters.