Commissioning and quality assurance of the Pinnacle(3) radiotherapy treatment planning system for external beam photons.

The commissioning of a Pinnacle3 treatment planning system is described. Four Elekta linear accelerators were commissioned for external beam photons. Measured data were used to derive parameter values for the Pinnacle3 beam model by (1) fitting a Monte Carlo model of the accelerator head to measured data and then extracting the parameters for the Pinnacle3 beam model, and by (2) using the auto-modelling facility within Pinnacle3. Both of these methods yielded dose distributions in accord with published recommendations. A separate small-field beam model, customized for an in-house compact blocking system, was also created, which satisfied appropriate acceptance criteria for stereotactically guided conformal brain treatments. Inhomogeneous, oblique, asymmetrical and irregular fields were also assessed, with calculated and measured doses agreeing to within ±3%. Dose–volume histogram calculation was found to be accurate to within ±5% dose or volume for a grid size of 4 mm × 4 mm × 4 mm, with better accuracy b...