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Develop and Evaluate a Non-Coplanar IMRT Treatment Plan Optimization System

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Y Li

Y Li1*, B Liu1 , T Song2 , S Xu3 , B Liang1 , X Xu1 , B Guo1 , R Wei1 , F Zhou1 , (1) Image Processing Center, Beihang University, Beijing, Beijing, (2) Southern Medical University, Guangzhou, Guangdong, (3) Chinese PLA General Hospital, Beijing


SU-I-GPD-T-325 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Treatment plans with non-coplanar beams have shown promise for the better dose avoidance of normal organs, which is favorable for stereotactic body radiation therapy (SBRT). Recently the CyberKnife M6 system was equipped with a multi-leaf collimator (MLC) to shape the beam, which is ideal for non-coplanar intensity modulated radiotherapy (IMRT) treatment compared with conventional LINACs. The purpose of this paper is to develop and evaluate a non-coplanar IMRT treatment plan optimization system.

Methods: A robotic radiosurgery system equipped with a multi-leaf collimator (MLC) was simulated based on CyberKnife system. The treatment nodes information was taken from clinical CyberKnife treatment plans. The plan optimization starts with none of beams, and conducts beam nodes selection and fluence map optimization (FMO) iteratively. For the treatment nodes selection, the norm of the negative gradient component of the objective function in the first iteration of the FMO problem formed by previously selected nodes and each candidate node was used to select the node. For the FMO problem, the total variation (TV) regularization term was added to reduce the complexity of the fluence pattern, therefore minimized the loss of plan quality after MLC leaf sequencing.

Results: For the tested lung patient which was originally planned with CyberKnife circular collimators, the non-coplanar IMRT plans reduced the maximum dose from 7.4Gy to 2.4Gy for spinal cord, and from 12.2Gy to 7.3Gy for esophagus. For the delivery efficiency, the non-coplanar IMRT plan consisted with 15 nodes and total 72 segments compared with 99 nodes for original circular collimator plan.

Conclusion: A non-coplanar IMRT treatment plan optimization system has been developed and evaluated by a lung case, which was proven to have better OAR dose sparing and higher delivery efficiency than original CyberKnife plan with circular collimators.

Funding Support, Disclosures, and Conflict of Interest: This work is supported by the National Natural Science Foundation of China (No.81601577,61601012),China Postdoctoral Science Foundation and the National Natural Science Foundation of China (No.2016M592510), and Southern Medical University School start-up fund(No.LX2016N0004)

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