Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada.
Department of Radiation Oncology, Dalhousie University, Halifax, Nova Scotia, Canada.
J Appl Clin Med Phys. 2020 Sep;21(9):16-24. doi: 10.1002/acm2.12958. Epub 2020 Jul 9.
This work introduces a novel capacitive-sensing technology capable of detecting respiratory motion with high temporal frequency (200 Hz). The system does not require contact with the patient and has the capacity to sense motion through clothing or plastic immobilization devices.
PURPOSE: This work presents and evaluates a novel capacitive monitoring system (CMS) technology for continuous detection of respiratory motion during radiation therapy. This modular system provides real-time motion monitoring without any contact with the patient, ionizing radiation, or surrogates such as reflective markers on the skin.
The novel prototype features an array of capacitive detectors that are sensitive to the position of the body and capable of high temporal frequency readout. Performance of this system was investigated in comparison to the RPM infrared (IR) monitoring system (Varian Medical Systems). The prototype included three (5 cm × 10 cm) capacitive copper sensors in one plane, located at a distance of 8-10 cm from the volunteer. Capacitive measurements were acquired for central and lateral-to-central locations during chest free-breathing and abdominal breathing. The RPM IR data were acquired with the reflector block at corresponding positions simultaneously. The system was also tested during deep inspiration and expiration breath-hold maneuvers.
Capacitive monitoring system data demonstrate close agreement with the RPM status quo at all locations examined. Cross-correlation analysis on RPM and CMS data showed an average absolute lag of 0.07 s (range: 0.03-0.23 s) for DIBH and DEBH data and 0.15 s (range: 0-0.43 s) for free-breathing. Amplitude difference between the normalized CMS and RPM signal during chest and abdominal breathing was within 0.15 for 94.3% of the data points after synchronization. CMS performance was not affected when the subject was clothed.
This novel technology permits sensing of both free-breathing and breath-hold respiratory motion. It provides data comparable to the RPM system but without the need for an IR tracking camera in the treatment room or use of reflective markers on the patient.
本研究介绍了一种新型电容监测系统（CMS）技术，用于连续监测放射治疗过程中的呼吸运动。该模块化系统可实时监测运动，无需与患者接触，无需使用电离辐射或皮肤反射标记等替代物。
新型原型设备由一组对身体位置敏感且能进行高频实时读取的电容探测器组成。该系统的性能通过与 RPM 红外（IR）监测系统（Varian Medical Systems）进行比较进行了评估。原型系统包括三个（5 cm×10 cm）位于同一平面的电容铜传感器，与志愿者的距离为 8-10 cm。在胸部自由呼吸和腹部呼吸时，对中央和中央向侧面位置进行电容测量。同时，在相应位置使用反射器块获取 RPM IR 数据。该系统还在深吸气和呼气屏气操作中进行了测试。
CMS 数据与所有检查位置的 RPM 现状数据密切一致。对 RPM 和 CMS 数据的互相关分析显示，DIBH 和 DEBH 数据的平均绝对滞后时间为 0.07 s（范围：0.03-0.23 s），自由呼吸的滞后时间为 0.15 s（范围：0-0.43 s）。在同步后，94.3%的情况下，胸部和腹部呼吸时 CMS 和 RPM 信号的归一化幅度差小于 0.15。当受试者穿着衣服时，CMS 性能不受影响。
这项新技术可感知自由呼吸和屏气呼吸运动。它提供的数据与 RPM 系统相当，但在治疗室中不需要 IR 跟踪相机，也不需要在患者身上使用反射标记。
