33. Dosimetry evaluation for VMAT breast and nodes treatment

Abstract

Introduction Feedback of VMAT breast and nodes dosimetry based of an international competition organized by the King Faisal Specialist Hospital & Research Centre (Saudi Arabia) in 2016, in order to develop the technic at the Clinical Center of Porte de Saint Cloud. Methods Treatment plans for breast and nodes have been realized with Pinnacle 9.10 TPS and for a Versa HD linac with Agility collimator (160 leafs). Dosimetry is optimized for different PTV and OAR constraints. Dosimetry has been evaluated with the competition parameters and with gamma index method (using PTW’s Octavius4D and Verisoft 6.2) to analyze the plan treatment feasibility on linac. A DVH comparison between VMAT and conformational dosimetry was also realized. Results Competition criteria have been successfully realized with 92% points of measure accept 4%/4 mm gamma index. Gamma index analyze show better results for less optimize treatment plans but worst competition score. VMAT dosimetry have better OAR protection and PTV uniformity and conformity than conformational dosimetry. Conclusions Competition allowed us better knowledge and mastery for breast VMAT. Dosimetry analyze show us that too much optimization are not able to be realized on the linac. Compromise must be define to perform the best VMAT dosimetry and make a feasible treatment on the linac. VMAT dosimetry improve DHV constraints and allow a shorter time treatment. Feedback of VMAT breast and nodes dosimetry based of an international competition organized by the King Faisal Specialist Hospital & Research Centre (Saudi Arabia) in 2016, in order to develop the technic at the Clinical Center of Porte de Saint Cloud. Treatment plans for breast and nodes have been realized with Pinnacle 9.10 TPS and for a Versa HD linac with Agility collimator (160 leafs). Dosimetry is optimized for different PTV and OAR constraints. Dosimetry has been evaluated with the competition parameters and with gamma index method (using PTW’s Octavius4D and Verisoft 6.2) to analyze the plan treatment feasibility on linac. A DVH comparison between VMAT and conformational dosimetry was also realized. Competition criteria have been successfully realized with 92% points of measure accept 4%/4 mm gamma index. Gamma index analyze show better results for less optimize treatment plans but worst competition score. VMAT dosimetry have better OAR protection and PTV uniformity and conformity than conformational dosimetry. Competition allowed us better knowledge and mastery for breast VMAT.