Combining the wavelet transform with a phase-lead compensator to a respiratory motion compensation system with an ultrasound tracking technique in radiation therapy

This study evaluated the feasibility of applying the wavelet transform (WT) combined with a phase-lead compensator (PLC) to our previously developed two-dimensional respiratory motion compensation system (RMCS). This system automatically and instantaneously adjusts PLC parameters according to different respiration signals to reduce influences of the system delay time, improving the compensation effect of the RMCS during respiratory motion compensation. This study performed respiratory movement compensation experiments with a two-dimensional respiratory motion simulation system (RMSS) and the RMCS. Human respiratory signals were captured using our previously developed ultrasound image tracking algorithm (UITA). In this study, a displacement compensation RMCS algorithm based on the combination of WT and PLC was developed by LabVIEW, which allows an automatic adjustment of the PLC parameters according to various respiratory waveforms, achieving a better compensation effect. The experiment results indicated that the compensation rate (CR) of right-left and superior-inferior directions had both improved 67.96–88.05% and 70.38–91.43%, respectively. In this study, the proposed method combined with WT and PLC applied in respiratory movement compensation experiments; the UITA was used for tracking diaphragm motion which substitutes for tumor motion. This noninvasive monitoring method also helps reduce side effects after treatment. The experimental results indicated that the effect of using the WT combined with the PLC to compensate for various respiratory signals was improved over our previously developed compensation algorithm.