- 學位論文
新穎聲阻隔共鳴結構應用於保護肋骨之超音波高能聚焦熱療系統建置
A novel Rib-sparing transcostal high-intensity focused ultrasound system based on resonant sound-blocking principle
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摘要
橫穿肋骨高強度聚焦超聲治療最主要的挑戰為避免將能量堆積在肋骨，並且能同時確保有足夠的熱劑量被遞送到目標區域。現今研究方法多仰賴昂貴的多通道相控陣列系統，利用換能器開關系統根據任意幾何形狀安排複雜的波形計算。此類型研究要注意到保護肋骨時，不僅須防止超聲波能量到達肋骨並要注意肋骨前方的能量堆積。本研究提出了一種不同的方法並建立一套治療系統，將聲結構放置於肋骨前使其具有相似於那些發動機的排氣消聲器效果。它的聲音阻擋結構是基於消音器原理，防止超聲波能量到達肋骨且不會導致過多的能量去反饋回探頭。在換能器驅動頻率為0.5 MHz下，有限元素的整體聲場和溫度分佈表示，新穎的聲音阻擋結構有效降低了結構正後方的超聲壓力和能量級別，因此肋骨比腫瘤的溫度還低。如果在沒有結構保護的情況下，肋骨溫度將會達到104.18℃，而有結構的情況只有37.86℃。此外，從豬的肋骨與仿體實驗所提出的驗證，結果顯示出該肋骨在沒有保護下只需一分鐘就達到72.80℃的燒融，而有保護的情況溫度僅36.39℃。而在腫瘤區域分別達到51.39℃，49.33℃。
並列摘要
The main challenge in transcostal high-intensity focused ultrasound therapy is minimizing heat deposition on the ribs while ensuring that a sufficient dose is delivered to the target region. Current approaches rely on expensive multichannel phased-array systems to turn individual transducer on and off according to either geometrical arrangements or complicated wave calculations. Notice that to protect the ribs from heating one must prevent the ultrasound energy not only from reaching the ribs but also from accumulating in front of the ribs. This research proposes a different approach to attach a sound-blocking structure with similar effects to those of the exhaust muffler of an engine in front of the rib cage and establish an ablation treatment system. The sound-blocking structure is designed based on the muffler principle to prevent the ultrasound energy from reaching the ribs while not causing too much energy to reflect back to the applicator. Finite-element simulations with 0.5 MHz transducer of the overall sound fields and temperature distribution showed that the ultrasound pressure and energy level decreases behind the novel sound-blocking structures, thereby achieving lower temperature on the ribs than on the tumor. Without the protecting structure the rib temperature reaches 104.19℃ while reaching only 37.86℃ with the structure. An experimental setup using porcine ribs with phantom was also developed to validate the proposed concept. The results showed that the rib temperature reached 72.80℃ without protection within only 1 minute of ablation time while maintained at 36.39℃ with the proposed device. The tumor region in the tests reached 51.39℃ and 49.33℃ respectively.
參考文獻
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