基於超音波成像之高強度聚焦式超音波熱治療監控

Ultrasound Imaging Based Monitoring of High Intensity Focused Ultrasound Thermal Therapy

黃聖閔(Sheng-Min Huang)

指導教授 ： 李夢麟

國立清華大學/電機資訊學院/電機工程學系所/博士(2019年)

摘要

高強度聚焦式超音波熱燒灼手術是一種將聲波能量聚焦於體內特定部位產生高熱，使組織細胞因熱凝結而壞死的非侵入性治療技術。臨床上主要採用磁振造影導引手術，以提高執行效率及安全性。然而，磁振造影除了有高成本、非即時性的缺點外，在病人的適用性上也有著嚴格的限制。特別是體內有磁性金屬植入物、配戴心律調節器或是有幽閉恐懼症的患者。因此，有必要開發新的監控技術，以彌補磁振造影的限制。
超音波造影是目前臨床上唯一同時具有高可靠度、低成本、可攜帶性、即時性、非游離性及高病人相容性等優勢的成像技術。因此，本研究以超音波成像為基礎，開發了三種監控技術，分別用於高強度聚焦式超音波熱燒灼手術的三個階段：術前規劃、術間導引及術後確認。對於術前規劃，本研究建議使用超音波溫度造影技術，追蹤溫升反應來定位聚焦點位置。並提出基於S形函式的改良式互相關演算法，解決傳統超音波溫度造影技術對於訊雜比與軸向解析度間的權衡問題。術後確認，則提出使用Nakagami參數影像來識別焦斑生成，以解決傳統超音波影像識別可靠度的問題。最後則提出，使用具有發射/接收操作的雙模高強度聚焦式超音波相控陣系統，搭配基於聲學傳遞系統模型的影像重建技術，重建發射聚焦波束。可望用於術間導引，持續監控焦點位置。
總結來說，本研究透過模擬、仿體及離體實驗證實，所提之三種成像技術可以分別滿足術前規劃、術間導引及術後確認三大目標。證明了以超音波成像為基礎的監控技術，用來導引手術執行是可行的。

關鍵字

聚焦式超音波熱治療 ； 超音波熱成像 ； S型函數 ； 互相關 ； Nagagami影像 ； 焦斑偵測 ； 模型式重建 ； 最小均方誤差

並列摘要

High intensity focused ultrasound (HIFU) thermal therapy is a non-invasive treatment technique focusing the ultrasound on the specific location of the inside body to concentrate energy and induce thermal coagulation. Currently, magnetic resonance imaging-guided HIFU (MRgHIFU) is mainly used in clinical treatment. However, MRgHIFU not only has limitations of high cost, slow imaging speed but also are not applicable for patients with claustrophobia, pacemakers, and ferromagnetic implants.
This study proposes three monitoring techniques based on ultrasonic imaging for HIFU thermal therapy which are used in the phases of preoperative planning, intraoperative guidance, and postoperative confirmation to compensate for the limitations of MRI. For preoperative planning, this study suggests using ultrasonic thermography to locate the focal point by tracking temperature change and proposes a sigmoid function based cross-correlation method to improve the axial resolution of the thermography without losing the signal-to-noise ratio. For postoperative confirmation, Nakagami imaging is proposed to identify the thermal lesion generated by HIFU. Compared to the traditional ultrasound B-mode image, Nakagami imaging not only can characterize the lesion effectively but also can avoid the misidentification of the bubbles formed during the treatment as the lesion. Finally, based on a dual-mode ultrasound phased array system supporting both transmit and receive operations, we propose an acoustic propagation model based beam reconstruction method to map the transmit focal beam for the goal of intraoperative guidance.
The results of simulations, phantom experiments, and ex vivo experiments demonstrate that the proposed methods could meet the goals for monitoring HIFU thermal therapy. It also proved the feasibility of ultrasound imaging based monitoring technology to guide HIFU thermal therapy.

並列關鍵字

High-intensity focused ultrasound thermal therapy ； Ultrasonic thermography ； Sigmoid function ； Cross-correlation ； Nakagami imagnig ； Lesion detection ； Model-based reconstruction ； Minimum mean-square error

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