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操作，以在患者呼吸时将外部放射治疗射束保持在目标上。Calypso系统使用小型电磁线圈，可以植入肿瘤中，然后通过位于患者上方的发射器/接收器系统以毫米级精度远程定位。这项技术最初是为了取代接受外照射放射治疗的患者的肿瘤部位的基于图像的定位，并在照射过程中提供连续跟踪。由于该系统可以以每秒十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。将通过表征Calypso测量系统的准确性和时间响应，设计和表征控制回路以将Calypso测量转换为射束控制数据同时调节系统滞后时间，然后根据自由呼吸期间肿瘤运动的测量临床数据评估完整的控制过程性能，来分析将实时跟踪应用于肺放射治疗的可行性。电磁肿瘤跟踪将补充并可能取代目前在治疗期间定位移动肿瘤所需的密集放射成像。这将导致对患者的非治疗性辐射剂量显著减少，同时简化肿瘤定位过程。增强的Calypso靶向系统将被设计成集成到现有的放射治疗系统中，以提供增强的射束靶向能力。

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.