Edge加速器Calypso4D电磁定位系统精确性评估

摘要

目的:研究Calyps0 4D电磁定位系统的几何精度和电磁阵列对加速器射线的衰减.方法:分别把植入式转发器和表面转发器安装在体模上,对比Calypso测量的体模等中心位移和实际位移,分析系统的定位精度;使用指型电离室测量有和没有电磁阵列时固体水内剂量,验证电磁阵列对射线的衰减;重复测量相同位置的体模等中心,评估系统稳定性.结果:植入式转发器的定位精度是(0.02±0.01) cm,表面转发器的定位精度是(0.01 ±0.01) cm;在机架角325°到35°范围内,6和10MV能量电磁阵列对加速器射束的衰减低于2％,在305°和55°衰减低于3.4％;重复测量时出现偏移的标准差在0.012 cm以内.结论:Calypso系统定位精度能够稳定在亚毫米级,电磁阵列对射线的衰减在临床接受范围内,Calypso 4D电磁定位系统是精确、可靠的,能够大大提高放疗精度.%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.