| Summary: | 碩士 === 國立臺北科技大學 === 機電整合研究所 === 104 === During radiation therapy, the respiration-induced tumor motion, changes in breathing patterns or sudden physiological responses such as cramps, yawning, sneezing, coughing, etc., cause a baseline shift. Thefore, the radiation treatment field size is not within the planning target volume (PTV), resulting in the suspension of treatment thus increasing the time and cost of radiation therapy.
This study aims to evaluate the feasibility of using an ultrasound image tracking algorithm (UITA) combined with a respiratory compensating system (RCS) to track and compensate the baseline shift of the diaphragm in real time. Diaphragm motion is observed with the previously developed UITA to perform the real-time diaphagrm tracking and a total of 15 different kinds of baseline shift patterns are selected through a large number of observational data. The captured baseline shift signals are analyzed to offset the diaphragm motion, and thus, reducing the happening of tumor baseline shift during the radiation therapy.
Diaphragm motions and various baseline shift signals of volunteers was tracked and captured by our previously developed UITA. In this study, a diaphragm phantom was placed on a respiratory simulation system (RSS), inputting with different kinds of baseline shift pattern signals, to simulate actual human baseline shift signals. The target displacement is automatically calculated by UITA and compensated by the RCS. In this study, the phantom displacements were observed under LINAC at Department of Radiation Oncology, Taipei Medical University Hospital, and the results were also compared with the displacements measured by UITA, RSS for correlation verification. In addition, and the compensating effect was analyzed after activing the RCS.
Experimental results indicate that the correlation between UITA calculated displacements and the actual displacement is up to 91% for the simulated respiration baseline shift signals. After activing the RCS, the obtained compensating effect was more than 65% and even up to 85% if a phase lead compensator (PLC) was used. Moreover, the compensation of a group of 10 extreme diaphragm baseline shift patterns has been improved significantly through the use of a PLC and the highest compensating rate of up to 88.92% was achieved. Finally, 10 volunteers were selected for the actual human trials and the results show that the compensation effect is in the range of 52% to 74%.
In this study, the ultrasound imaging tracking technology combined with the RCS is a radiation-therapy aid with a simple mechanism, easy to set up, and offset the respiration-induced organ displacement through a non-invasive ultrasound image system. It not only accurately targets the tumor displacement, nearby the diaphragm, but also enables the operator to instantly observe the baseline shift phenomenon of the tumor and compensate simultaneously. Even if a baseline shift occurs, the radiological instrument is still running without interruption, and thus, it does not affect the overall treatment time.
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