Purpose: To verify a collapsed cone (CC) dose calculation algorithm used for secondary treatment planning checks based on TG-219 recommendations. This commercially available software is used to second check a treatment planning system (TPS) dose distribution on CT datasets.
Methods: A vendor supplied CC dose engine was installed and modelled with measured data for a 6 MV photon beam. A point dose comparison on a set of photon fields was compared between the secondary check software and ion chamber measurements in water phantom. Open fields on a phantom dataset with heterogeneous slabs were also compared between the second check software and TPS. VMAT plans developed based on TG-119/TG-224 datasets/criteria were also compared to the TPS by point dose evaluation and gamma analysis (3%/3mm). wellll
Results: For open field point dose measurements, the average deviation between ion chamber measurement and calculation was found to be –0.32%±0.21%. For the heterogeneity correction tests, the average agreement was 0.1%±0.28%. For the TG-119/TG-214 datasets, the average composite gamma pass rate is 97.6%±2.6% with a point dose average deviation of –1.8%±2.03%. For individual field measurements, the average composite gamma passing rate is 97.84%±1.9%, with a point dose deviation of –1.9%±3.13%
Conclusion: The second check software was found to meet passing criteria and is considered for clinical implementation. The process did prove challenging to get the TPS data transferred to the second check system for the individual VMAT field comparison. Further testing will be performed across all clinical energies.
Collapsed Cone Superposition, X Rays, Commissioning
TH- External Beam- Photons: Computational dosimetry engines- deterministic