超音波影像追蹤技術結合自動調控腫瘤定位系統之可行性評估

本研究目的為評估超音波影像分析技術結合自動調控腫瘤定位系統之可行性。由於呼吸運動會造成人體肺下葉與緊鄰肺下葉器官之位移，其中又以頭腳向的位移範圍最大，本研究定位腫瘤方式採以頭腳向的呼吸補償，就肺下葉及緊鄰肺下葉之器官進行呼吸位移補償。鑒於呼吸訊號經超音波成像、影像分析與訊號傳輸過程有所延遲，本研究經一系列分析實驗，確立訊號傳輸處理之總延遲時間為0.254+0.023秒。為了彌補訊號之延遲時間，本研究於腫瘤定位系統的控制法則中設計領先補償器。藉由分析延遲時間及不同頻率的呼吸波形對領先補償器所造成的影響，發現固定整體系統的延遲時間，隨著呼吸頻率上升，控制器內的變數a值與後續的增益變大；當呼吸頻率固定，提高待整體系統的延遲時間，變數值a與後續的增益隨之提升。再以迴歸建表之方法，可獲得變數a值、後續增益分別與呼吸頻率之關係，用以進行呼吸補償的腫瘤定位。最終透過未補償之模擬呼吸訊號與自動調控補償後之訊號比較，以評估超音波影像分析技術結合自動調控腫瘤定位系統之可行性。其結果發現模擬呼吸訊號在不同的頻率0.5、0.333、0.25、0.2及0.167 Hz下經過領先補償器後，均有改善且具有相當穩定的結果。其中補償率提升範圍為7.04~18.82%，最後補償效果皆約為97%左右，故以超音波影像分析技術結合自動調控腫瘤定位系統是可行的。本研究研發之超音波影像分析技術結合自動調控腫瘤定位系統具有以下四點優勢：1. 使用非侵入式觀察器進行主動式呼吸補償，無需使用有劑量之照影方式觀察體內器官之位移。2. 放射線治療過程中，結合自動調控腫瘤定位系統，可不間斷的進行治療，不影響整體治療時間。3. 自動調控腫瘤定位系統為獨立系統，可裝置於任一治療平台。4.使用者無須進行繁雜的操作，即可進行自動呼吸定位補償之功能。

關鍵字

即時追蹤；呼吸運動補償；超音波；領先補償

並列摘要

The purpose of this study is to evaluate the feasibility assessment of the auto tuning respiratory compensation system with ultrasonic image tracking technique. According to the respiratory motion, the maximum range of organ displacement surrounding the lower lobe of lung is Superior-Inferior. The SI direction is issued with respiratory compensation in this study. However, there is respiratory signal delay in the system through generating ultrasound image, image processing, and signal transferring. For compensating the signal delay time, this study approaches the design of phase-lead compensator in the controller. There are two variants, variable “a” and gain of compensator, in the design of phase-lead compensator. When fixing the delay time for compensating, the variants will increase as the frequency of respiratory signal raise up. When fixing the frequency of respiratory signal, the variants will also increase as the delay time raise up. Before design of phase-lead compensator, we analyzed the system delay and concluded the respiratory delay time as 0.254+0.023 seconds in this study. For evaluating the feasibility assessment of the auto tuning respiratory compensation system with ultrasonic image tracking technique, there are 5 different frequencies of sine wave for simulating the respiratory signal as 0.5, 0.333, 0.25, 0.2, and 0.167 Hz. According to the varying frequency of sine wave, we tuned the variants of the compensator through the relationship of curve fitting. The conclusion is the rate of compensating the respiratory motion is stable and improved through phase-lead compensator. The rate of compensation promotes to 7.04-18.82% rather than without compensator, and the average of the compensation rate is approximately 97%. As a result, the auto tuning respiratory compensation system with ultrasonic image tracking technique is feasible. The advantages of the auto tuning respiratory compensation system as follows: 1. Non-invasive ultrasound sensor for active respiratory compensation. 2. Continuously radiotherapy treatment with this system. 3. Independent system suited for any treatment couch. 4. Operating easily for auto tuning respiratory compensation system.

並列關鍵字

real-time tracking ； compensated respiratory motion ； ultrasound image tracking ； phase lead compensator

參考文獻

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超音波影像追蹤技術結合自動調控腫瘤定位系統之可行性評估

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