Wang Yongqiang, Li Bing, Xiao Xuhua, Lou Zhaoyang, Liu Kangdong, Ge Hong
The Affiliated Cancer Hospital of Zhengzhou University & Henan Cancer Hospital Zhengzhou China.
School of Electronic Engineering North China University of Water Resources and Electric Power Zhengzhou China.
Precis Radiat Oncol. 2025 Dec 15;9(4):251-259. doi: 10.1002/pro6.70037. eCollection 2025 Dec.
This study aimed to improve the accuracy of the tumor radiotherapy dose and reduce the irradiation dose to the surrounding organs, by developing a versatile respiratory motion monitoring system with multi-scenario applications to enhance the clinical efficacy of radiotherapy for thoracic and abdominal tumors.
The respiratory motion monitoring system comprised an airbag structure integrated with a parallel-plate capacitive sensor. The airbag comprised a polymer balloon encapsulated in a nonelastic flexible membrane, and had a projected area of 120 mm × 120 mm. The capacitive sensor adopts a concentric configuration of beryllium copper (thickness: 0.1 mm, diameter: 10 mm) and oxygen-free copper (thickness: 1 mm, diameter: 10 mm) foils. Real-time monitoring of the respiratory motion was achieved by detecting the capacitance variations corresponding to changes in the internal air pressure within the airbag. The system performance was rigorously evaluated using a dynamic thorax phantom capable of simulating various patterns, including sinusoidal and fourth-power cosine waveforms.
The capacitive sensor-based respiratory motion monitoring system demonstrated a displacement measurement range of up to 10 mm, capable of detecting movements as small as 0.1 mm (signal-to-noise ratio: 2.18). Real-time displacement conversion was performed using the fitted model = a+b (a = 26.105 ± 0.398, b = 285.868 ± 22.147). The system exhibited a high stability, with a standard deviation of only 0.0011 in capacitance measurements over 10 repeated tests with a 5 mm amplitude sinusoidal waveform, and further maintained the amplitude consistency within 2.25%-96.05% of the maximum value throughout 10 min of continuous operation. A reliable performance was confirmed across various respiratory waveforms, including sinusoidal and fourth-power cosine profiles. Furthermore, the non-metallic airbag structure enhances the adaptability to multiple clinical scenarios. However, two types of signal distortions were observed, originating from the airbag deformation and the limitations of the capacitive sensor electrode, both of which are thoroughly explained in the manuscript.
Overall, this study developed a capacitive sensor and airbag-based respiratory monitoring system that combines the advantages of abdominal pressure belts with infrared-based monitoring technologies. This integrated approach offers a cost-effective, structurally simple, and versatile solution for monitoring respiratory motion across multiple clinical scenarios.
本研究旨在通过开发一种具有多场景应用的通用呼吸运动监测系统，提高胸部和腹部肿瘤放射治疗的临床疗效，从而提高肿瘤放疗剂量的准确性并减少对周围器官的照射剂量。
呼吸运动监测系统包括一个与平行板电容式传感器集成的气囊结构。气囊由封装在非弹性柔性膜中的聚合物气球组成，投影面积为120 mm×120 mm。电容式传感器采用铍铜（厚度：0.1 mm，直径：10 mm）和无氧铜（厚度：1 mm，直径：10 mm）箔的同心配置。通过检测与气囊内气压变化相对应的电容变化来实现对呼吸运动的实时监测。使用能够模拟各种模式（包括正弦和四次幂余弦波形）的动态胸部体模对系统性能进行了严格评估。
基于电容式传感器的呼吸运动监测系统显示出高达10 mm的位移测量范围，能够检测低至0.1 mm的运动（信噪比：2.18）。使用拟合模型 = a + b（a = 26.105 ± 0.398，b = 285.868 ± 22.147）进行实时位移转换。该系统表现出高稳定性，在5 mm振幅正弦波形的10次重复测试中，电容测量的标准偏差仅为0.0011，并且在连续运行10分钟内，振幅一致性保持在最大值的2.25% - 96.05% 以内。在包括正弦和四次幂余弦轮廓在内的各种呼吸波形中均证实了可靠的性能。此外，非金属气囊结构增强了对多种临床场景的适应性。然而，观察到两种类型的信号失真，分别源于气囊变形和电容式传感器电极的局限性，手稿中对这两种情况都进行了详细解释。
总体而言，本研究开发了一种基于电容式传感器和气囊的呼吸监测系统，该系统结合了腹部压力带和基于红外监测技术的优点。这种集成方法为在多种临床场景下监测呼吸运动提供了一种经济高效、结构简单且通用的解决方案。
