Abstract

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Title:: Evaluation of the accuracy of Calypso 4D electromagnetic localization system in Edge accelerator

Author(s):: DAI Zhenhui1; ZHANG Bailin1; ZHU Lin1; ZHU Yuanhu1; YANG Geng1; CAI Chunya1; LI Fei1; ZHANG Yu2; WANG Xuetao1; 1. Department of Radiation Therapy, Guangdong Provincial Hospital of Traditional Chinese Medicine, Guangzhou 510006, China;
2. School of Biomedical Engineering, Southern Medical University, Guangzhou 510515, China

Abstract:: Objective To evaluate the geometric accuracy of Calypso 4D electromagnetic localization system and study the attenuation of ray caused by electromagnetic array. Methods Implantable transponders and superficial transponders were placed in the phantom, separately. The localization precision was analyzed by comparing the displacement of the phantom isocenter measured with Calypso and actual displacement, and the attenuation of ray caused by electromagnetic array was evaluated by measuring the dose of solid water with and without electromagnetic array. The phantom isocenter at the same position was measured repetitively for assessing the system stability. Results The accuracies of implantable and superficial transponders were (0.02[±0.01]) cm and (0.01[±0.01]) cm. The attenuation caused by electromagnetic array was below 2% for both 6 MV and 10 MV energies at gantry angles between 325° and 35°, and was lower than 3.4% at gantry angles of 305° and 55°. The standard deviation of displacement was within 0.012 cm in repeated measurements. Conclusion The accuracy of Calypso localization system is steadily at submillimeter level, meanwhile, the attenuation of ray caused by electromagnetic array is clinically insignificant. Calypso 4D electromagnetic localization system which is accurate and reliable can greatly improve the accuracy of radiotherapy.