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VMAT Planning and Delivery of Challenging GI/GYN Cases Using Varian True Beam HD MLC

N Kalach1*, E Sudentas2 , (1) Mount Sinai West, New York, NY, (2) Mount Sinai West, New York, NY


(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: VMAT treatment technique was implemented on a Varian TrueBeam STx linac with High Definition (HD) MLC. Treatment planning and delivery for GI/GYN cases with nodal involvement presented a challenge due to HD MLC field size limitation. Creative method of the treatment planning using multi-arc combinations was developed. Clinical database of the previously treated cases was established to assist for efficient planning and training purposes.

Methods: Varian Eclipse treatment planning system was used for planning VMAT cases with target length up to 36 cm and target width up to 28 cm. The hard criteria for planning technique was keeping Y-jaw size under 22 cm due to MLC limitation. The feasibility of the planning approach was tested and method was implemented for more than 15 patients during one year time. Average target length treated was 29 cm and average target width 21 cm with varying plan complexity. All clinical plans were reviewed and approved by physicians according to standard dose constraints and plan quality criteria. Pretreatment QA was completed for all clinical plans according to department procedure using IBA MATRIXX and/or Varian Portal Dosimetry and passed standard criteria. Clinical database of the challenging VMAT cases was created to serve as a knowledge base for all new cases and training purposes.

Results: Feasibility of the VMAT treatments of the large GI/GYN volumes on Varian True Beam STx linac with HD MLC was tested and technique was implemented for a number of clinical cases. Database of the sample plans was created to increase planning efficiency and for the training purposes.

Conclusion: We have proven feasibility of VMAT on the SRS-dedicated linac with HD MLC and treated a number of challenging GI/GYN cases thus increasing the robustness of the clinical use of the linac.


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