Electromagnetic Tracking of Tumors for Radiotherapy

描述（由申请人提供）：本项目将分析使用Calypso电磁定位系统跟踪随呼吸移动的肿瘤的可行性。这种能力将允许系统通过控制回路运行，在患者呼吸时保持外部放射治疗光束对准目标。Calypso系统使用小型电磁线圈，可以植入肿瘤中，然后通过放置在患者上方的发射器/接收器系统远程定位，精度达到毫米级。这项技术最初是为了替代基于图像的肿瘤部位定位，用于接受外束放疗的患者，并在放疗过程中提供连续跟踪。由于该系统可以以每秒10次测量的速率对肿瘤位置进行采样，因此原则上能够实时跟踪肿瘤。通过表征Calypso测量系统的准确性和时间响应，设计和表征控制回路，在适应系统滞后时间的情况下将Calypso测量结果转化为光束控制数据，然后根据自由呼吸期间肿瘤运动的测量临床数据评估整个控制过程的性能，分析将实时跟踪应用于肺部放疗的可行性。电磁肿瘤跟踪将补充并有可能取代目前需要在治疗过程中定位移动肿瘤的强化放射成像。这将导致对患者的非治疗性辐射剂量的显著减少，同时简化肿瘤定位过程。增强的Calypso靶向系统将被设计用于集成到现有的放射治疗系统中，以提供增强的光束靶向能力。

DESCRIPTION (provided by applicant): This project will analyze the feasibility of using the Calypso electromagnetic localization system to track tumors that move with breathing. Such a capability will allow the system to operate through a control loop to keep an external radiation therapy beam on target while the patient breathes. The Calypso system uses small electromagnetic coils that can be implanted in a tumor and then located remotely, with millimeter-scale accuracy, by a transmitter/receiver system positioned above the patient. This technology was initially developed to replace image-based localization of the tumor site for patients undergoing external-beam radiotherapy, and to provide continuous tracking during the course of irradiation. Because the system can sample the tumor position at a rate of ten measurements per second, it is capable in principle of real-time tumor tracking. The feasibility of applying real-time tracking to lung radiotherapy will be analyzed by characterizing the accuracy and time response of the Calypso measurement system, designing and characterizing a control loop to translate the Calypso measurement into beam control data while accommodating system lag time, and then assessing the complete control process performance against measured clinical data for tumor motion during free breathing. Electromagnetic tumor tracking will supplement and potentially replace the intensive radiological imaging that is presently needed to locate moving tumors during treatment. This will result in a significant reduction in non-therapeutic radiation dose to the patient while simplifying the tumor localization process. The augmented Calypso targeting system will be designed for integration into existing radiation therapy systems to provide enhanced beam targeting capability.