以超音波影像同步追蹤由呼吸導致之肝腫瘤運動

Abstract

在近年的研究中，核磁共振影像導引的高強度聚焦型超音波熱療系統在治療靜態腫瘤中獲得不錯的治療效果。然而在治療動態腫瘤上，由於用於定位動態腫瘤的核磁共振影像成像速度只有7 Hz，無法達到即時的定位追蹤加熱治療，例如肝癌與肺癌。 本研究目標為建立一套由超音波影像導引的同步系統，將可應用於肝臟腫瘤的高強度聚焦型超音波加熱治療。超音波影像的成像速度高達17 Hz，足以即時的同步追蹤肝腫瘤，並具有低成本與無副作用等優點。然而超音波影像有厚度方向定位誤差與低解析度等缺點，因此本研究針對肝臟移動軌跡具有一個明顯移動主軸的特性，提出了一套超音波影像校正與同步的方法，以降低超音波影像的厚度定位誤差並與肝臟腫瘤的運動進行同步運動。為了實現本研究提出的方法，本論文建構了具有六個自由度的機械手臂，能實現超音波影像在厚度方向上校正所需的各種角度與進行三維空間的同步運動。在以直徑為10 mm的塑膠珠實驗中，超音波影像厚度校正平均誤差為1.2度與0.4 mm；同步的方均根誤差均小於1.24 mm。相信此研究對於將來在以超音波影像導引的超強度聚焦型超音波熱療肝腫瘤上有一定程度的貢獻。

In recent studies, magnetic resonance image-guided high intensity focused ultrasound thermotherapy system has been proposed for the static tumors such as breast tumors and uterine fibroid tumors. However, it is very difficult to achieve real-time tracking thermotherapy by magnetic resonance image in mobile tumors, such as liver tumors and lung tumors. It is because the frame rate of the magnetic resonance image is only 7 Hz, which is not sufficient for real-time tracking. Therefore, this study is aimed at developing an ultrasound image-guided synchronization system. It can be applied to ultrasound image-guided high intensity focused ultrasound thermotherapy system for liver tumor. Compare to the magnetic resonance image, the ultrasound image has the advantage of high speed, low cost, and no harm to human body. However, ultrasound image has the shortage of slice thickness effect. This study bases on the characteristics of liver movement, and proposes the alignment and synchronization methods to reduce the slice thickness effect of ultrasound image. In order to realize the proposed alignment and synchronization methods, the six degree of freedom robot arm is built on the therapeutic system. The six degree of freedom robot arm is built based on the size and the movement of human liver. The alignment and synchronization experiments are done under the plastic ball experiments. The average alignment error is 1.2 degree and 0.4 mm. The synchronization errors are below 1.24 mm. It is believed that this study can apply to the real-time ultrasound image-guided high intensity focused ultrasound thermotherapy system for liver tumors.