SU‐E‐T‐766: Treatment Planning Comparison Study On Two Different Multileaf Collimators Delivered with Volumetric Modulated Arc Therapy

Purpose:To compare and evaluate the performance of two different multileaf collimators(MLCi2 and Agility) delivery with volumetric modulated arc therapy techniques.Methods:Treatment plans were graded four (Low, Moderate, Moderate‐High and High complexity) accorrding to the complexity. This includes 1 Low complexity(brain metastasis), 2 Moderate complexity(Lung and Liver), 1 Moderate‐High complexity(prostate) and 1 High complexity ( head and neck) cases. Total dose of 60 Gy was given for all the plans. All cases were desigined two VMAT plans, one with MLCi2(group A) and the other with Agility(group B). All plans were done on Elekta VMAT with Monaco treatment planning system. All plans were generated with 6 MV X‐rays for both Plan A and Plan B. Plans were evaluated based on the ability to meet the dose volume histogram, radiation conformity index, estimated radiation delivery time, dose homogeneity index(HI) and monitor units(MU) needed to deliver the prescribed dose.Results:Plans of group B achieved the best HI (HI = 1.05 Vs. 1.06) at the Low complexity cases while plans of group A were slightly better at the high complexity cases (HI = 1.12 Vs. 1.14). Faster VMAT plan delivery with Agility than with MLCi2 as plan complexity increased (Low complexity:52s Vs.52s, Moderate complexity:58s Vs. 55s, Moderate‐High complexity: 171s Vs.152s, High complexity : 326s Vs. 202s ), especially for the most complex paradigms delivered time can be decresed 38%. No Significant changes were observed between the group B and group A plans in terms of the healthy tissue mean dose and MU. Both plans respected the planning objective for all organs at risk.Conclusion:The study concludes that VMAT plans with the novel Agility MLC can significant decrease the delivering time at the high complexity cases, while a slight compromise in the dose homogeneity index should be noted.This work was supported by The Medical Science Foundation of The health department of Hebei Province (No. 20130253)