The respiratory compensation auto tuning system with ultrasound image tracking technique

• Main Authors: Kuan-Ting Teng, 鄧貫廷
• Other Authors: 莊賀喬
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/728bcu

碩士 === 國立臺北科技大學 === 機電整合研究所 === 103 === The purpose of this study is to develop a dynamic image processing algorithm, which can process the ultrasound images to extract the exact displacement of internal organs caused by respiratory motion. The real-time ultrasound images of the organs displacement can be tracked by using our proposed dynamic image processing program, and the tracked displacement signals are analyzed to offset organ displacement via a respiratory compensating system. Meanwhile, ultrasound imaging system is a non-invasive, good resolution, and with a relative high frame rate, which prevents patients from receiving unnecessary dose under observation of radiation. Thus, the non-invasive observation and the compensation of organ displacements can be simultaneously achieved during the entire radiation therapy. In this study, the ultrasound probe is used to replace 4D CT as a monitor to reduce the unnecessary radiation dose. However, there is respiratory signal delay in the system then generating ultrasound image, image processing, and signal transferring. We first analyzed the system delay and concluded the respiratory delay time as 0.176+0.029 seconds in this system. For compensating the signal delay time, this study designed the phase-lead compensator in the controller. Then a dynamic image tracking algorithm was designed for tracking specific target (such as diaphragm) motion. A simulated diaphragm motion driven by a respiratory simulation system (RSS) was observed with an ultrasound imaging system, and then the ultrasound images of the diaphragm displacements caused by the simulated respiratory signals were captured by our proposed image tracking algorithms. The diaphragm moving distances were calculated according to the algorithm, which can be used as the input signals to adjust the gain of RCS, so that the amplitude of the compensation signals are close to the target movement. In addition, the inclined angle of the ultrasound probe with respect to the body surface of the abdomen affects the results of ultrasound images tracking displacement. Therefore, in this study the displacement of the phantom was observed under a linear accelerator (LINAC), and verified with different inclined angle setup of the ultrasound probe. The experimental results indicate that the best inclined angle of the ultrasound probe is 40 degrees, which results in the target displacement of the ultrasound images close to the actual target motion. Finally through our proposed algorithms, the displacement signals of the tracking phantom and the reverse displacement signals created by the RCS were compared, and thus, the positioning accuracy of our ultrasound dynamic image tracking technique combines of RCS are assessed. The results show that when the ultrasound image tracking technique is used with the ultrasound probe placed in an inclined angle of 40 degrees for the simulated respiratory (sine wave) experiments, and the correlation between the target displacement on the ultrasound images and the actual target displacement was around 97%. Moreover, all of the compensation rates were more than 94% after activating the RCS. Furthermore, the human trials were performed from three patients, and their diaphragm movements on the ultrasound images were captured by our image tacking technique, whereby testing the adaptability of the image tracking algorithms for different ultrasound images of human internal organs. Testing results show that our algorithms are able to perform the precise point locking and tracking functions on diaphragms under different ultrasound images of human organs. Therefore, the proposed ultrasound image tracking technique combined with RCS for offsetting organ displacement due to respiratory motion is feasible.