Kuo Chia-Chun, Chuang Ho-Chiao, Liao Ai-Ho, Yu Hsiao-Wei, Cai Syue-Ru, Tien Der-Chi, Jeng Shiu-Chen, Chiou Jeng-Fong
Department of Radiation Oncology, Taipei Medical University Hospital, Taipei, Taiwan.
Department of Radiation Oncology, Wanfang Hospital, Taipei Medical University, Taipei, Taiwan.
Quant Imaging Med Surg. 2020 May;10(5):907-920. doi: 10.21037/qims.2020.03.19.
The reduction of the delaying effect in the respiratory motion compensation system (RMCS) is still impossible to completely correct the respiratory waveform of the human body due to each patient has a unique respiratory rate. In order to further improve the effectiveness of radiation therapy, this study evaluates our previously developed RMCS and uses the fast Fourier transform (FFT) algorithm combined with the phase lead compensator (PLC) to further improve the compensation rate (CR) of different respiratory frequencies and patterns of patients.
In this study, an algorithm of FFT automatic frequency detection was developed by using LabVIEW software, uisng FFT combined with PLC and RMCS to compensate the system delay time. Respiratory motion compensation experiments were performed using pre-recorded respiratory signals of 25 patients. During the experiment, the respiratory motion simulation system (RMSS) was placed on the RMCS, and the pre-recorded patient breathing signals were sent to the RMCS by using our previously developed ultrasound image tracking algorithm (UITA). The tracking error of the RMCS is obtained by comparing the encoder signals of the RMSS and RMCS. The compensation effect is verified by root mean squared error (RMSE) and system CR.
The experimental results show that the patient's respiratory patterns compensated by the RMCS after using the proposed FFT combined with PLC control method, the RMSE is between 1.50-5.71 and 3.15-8.31 mm in the right-left (RL) and superior-inferior (SI) directions, respectively. CR is between 72.86-93.25% and 62.3-83.81% in RL and SI, respectively.
This study used FFT combined with PLC control method to apply to RMCS, and used UITA for respiratory motion compensation. Under the automatic frequency detection, the best dominant frequency of the human respiratory waveform can be determinated. In radiotherapy, it can be used to compensate the tumor movement caused by respiratory motion and reduce the radiation damage and side effects of normal tissues nearby the tumor.
呼吸运动补偿系统（RMCS）中延迟效应的减少仍无法完全校正人体的呼吸波形，因为每个患者都有独特的呼吸频率。为了进一步提高放射治疗的有效性，本研究评估了我们先前开发的RMCS，并使用快速傅里叶变换（FFT）算法结合相位超前补偿器（PLC）来进一步提高不同呼吸频率和模式患者的补偿率（CR）。
在本研究中，使用LabVIEW软件开发了一种FFT自动频率检测算法，将FFT与PLC和RMCS相结合以补偿系统延迟时间。使用25名患者预先记录的呼吸信号进行呼吸运动补偿实验。实验期间，将呼吸运动模拟系统（RMSS）放置在RMCS上，并使用我们先前开发的超声图像跟踪算法（UITA）将预先记录的患者呼吸信号发送到RMCS。通过比较RMSS和RMCS的编码器信号获得RMCS的跟踪误差。通过均方根误差（RMSE）和系统CR验证补偿效果。
实验结果表明，使用所提出的FFT与PLC控制方法后，RMCS补偿的患者呼吸模式在左右（RL）和上下（SI）方向上的RMSE分别在1.50 - 5.71和3.15 - 8.31毫米之间。RL和SI方向上的CR分别在72.86 - 93.25%和62.3 - 83.81%之间。
本研究将FFT与PLC控制方法应用于RMCS，并使用UITA进行呼吸运动补偿。在自动频率检测下，可以确定人体呼吸波形的最佳主导频率。在放射治疗中，它可用于补偿呼吸运动引起的肿瘤运动，并减少肿瘤附近正常组织的辐射损伤和副作用。
