Session Item

Beam data acquisition for RayStation was performed at fixed SSD, and included percent depth dose (PDD), profiles at 15, 50, 100 and 300 mm depth, a single diagonal for the largest field, and output factors (OF). A microDiamond detector 60019 and a Beamscan water tank (PTW, Freiburg, Germany) were used for all measurements. Output factors (OF) were double-checked with a microSilicon detector (60023, PTW) and not adjusted by Monte Carlo (MC) correction factors. Beam modelling was performed for collapsed cone (CC) and MC algorithms for all collimators, except for the iris 5-mm aperture that cannot be modelled in RayStation. Validation tests for the quality of beam modeling were performed following the AAPM Practice Guideline 5.a. This included: a verification of the dose calculated in calibration conditions, comparisons of calculated dose distributions with commissioning data, comparisons of calculated dose distributions with 2D detector array measurements (Octavius 729 2D-Array, PTW), measurements for various MLC-shaped fields and fields at oblique incidence, and comparison of calculated dose in an heterogeneous medium with dose measurements in bone and lung inserts of a thorax phantom (CIRS, VA, USA). 

Beam data acquisition and processing for RayStation took approximately seven days (vs. 11 days for Precision). Calculated dose in reference conditions (only available through scripting in RayStation) was below 0.3% compared to calibration. Comparison between commissioning data and clinical dose calculated in a homogeneous phantom with CC showed that more than 97% of PDD and profile points respected gamma criteria of 1%/1mm (global), except for the iris aperture of 7.5 mm, the MLC smallest field, and at the depth 300 mm. The agreement increased when modeling the beam with MC algorithm, which also improved the beam modeling in the profile tails of the largest fields. MLC fields measured with the 2D detector at perpendicular and oblique incidence all agreed with TPS calculation within gamma 1.5%/1.5mm criteria. Differences between calculated and measured doses in the heterogeneous phantom were below 2% in the lung and bone inserts, for both CC and MC algorithms. 

RayStation 11A TPS for CK was successfully commissioned for clinical use in our department. Preliminary results show promising planning capabilities for stereotactic treatment planning with the CK S7.