(Tuesday, 7/31/2018) 3:45 PM - 4:15 PM
Room: Exhibit Hall | Forum 4
Purpose: This study utilizes the DoE to evaluate the VMAT planning parameters of single isocenter treatment plans for multiple brain metastases. An optimization model based on Design of Experiments coupled with Weighted Principle Component Analysis employed to optimize the planning parameters including: arc arrangement, calculation grid size, calculation model, and beam energy on multiple performance characteristics, namely conformity index and dose to normal brain.
Methods: Treatment plans, each with 4 metastatic brain lesions were planned using single isocentertechnique. The collimator angles were optimized to avoid open areas. In this analysis, fourplanning parameters (a-d) were considered: (a)-Arc arrangements: set1: Gantry 181cw179, couch0; gantry179ccw0, couch315; and gantry0ccw181, couch45. set2: set1 plus additional arc: Gantry 0cw179,couch270. (b)-Energy: 6-MV; 6MV-FFF (c)-Calculation grid size: 1mm; 1.5mm (d)-Calculation models: AAA; Acuros Treatment planning was performed in Varian Eclipse (ver.11.0.30). A suitable orthogonal array was selected (L8) to perform the experiments. After conducting the experiments with thecombinations of planning parameters, the conformity index (CI) and the normal brain dose S/N ratio for each parameter was calculated. Optimum levels for the multiple response optimizations were determined.
Results: We determined that the factors most affecting the conformity index are arc arrangement and beamenergy. These tests were also used to evaluate dose to normal brain. In these evaluations, thesignificant parameters were grid size and calculation model. Using the Weighted Principle Component we determined the combination of each of the four factors tested in this study that most significantlyinfluence quality of the resulting treatment plans:(a)-arc arrangement-set2, (b)-6MV, (c)-calc.grid1mm, (d)-Acuros algorithm. Overall, the dominant significant influences on plan quality are (a)-arcargument, and (b)-beam energy.
Conclusion: The optimization with DoE coupled with Weighted Principle Component Analysis is expected to found the reasonable solution efficiently.these results indicate the effectiveness of this strategy for clinical usage.
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