Room: Exhibit Hall
Purpose: A novel ring-type gantry radiotherapy machine equipped with a 6MV linac, a kV CBCT and a multileaf collimator has been developed for both intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). In this study we evaluate a treatment planning system for this new machine for prostate treatments.
Methods: The CyberMat MLC has 60 paired leaves, and the maximum field size is 40cmx40cm (40 pairs of 0.5cm central leaves, 20 pairs of 1cm outer leaves). For this study, CTs of 10 previously treated prostate patients were achived. The RT Pro planning system (version 1.00.4557, Prowess, Concord, CA) was used for treatment planning with the new system. Eclipse (Elekta CMS software, St. Louis, MO) was used to generate plans for the same patients on a Varian IX machine. Treatment plans for the two systems were evaluated based on isodose distributions and dose volume histograms. The Prowess planning system employs an aperture-based optimization algorithm while Eclipse uses a beamlet-based approach. Both systems apply dose-volume objectives for the target and critical structures of concern. These objectives are used as the criteria for the optimization. Both use two types of dose volume objectives: lower and upper objectives.
Results: Comparable planes were achieved in most cases. Based on our studied cases, larger hot spot in the PTV was seen with the aperture-based algorithm. However, this was of less concern with SBRT cases. Direct-aperture optimization could arrive at an optimal solution but would require longer optimization time and interactive adjustment of weighting factors for the different objective constrains. A machine learning option was tested to reduce efforts for planning interactions.
Conclusion: The Prowess system produced prostate plans that could meet our clinical acceptation criteria for the CyberMat delivery system.
Treatment Planning, Intensity Modulation
TH- External beam- photons: IMRT dose optimization algorithms