脈衝式磁致動超音波(pMMUS)為近年來發展用來監測超順磁性氧化鐵奈米粒子(SPIO Nanoparticles)的新式超音波成像技術，實現了傳統超音波影像無法觀測超順磁性氧化鐵奈米粒子的問題。但因磁脈衝的限制，目前技術通常僅能使用單一探頭搭配機械掃描方式進行成像，其成像速度大幅受限，不適合臨床使用。在本研究中我們提出了基於超快平面波成像之脈衝式磁致動超音波影像技術來解決此問題。利用僅需單一發射次數的平面波超快成像技術解決傳統陣列成像無法在磁脈衝產生時完成造影的問題。如此快速的成像可以在短磁脈衝下偵測超順磁性氧化鐵奈米粒子受到磁場作用產生振動的動態變化情形。此動態變化情形有機會反應組織的特性，像是組織彈性(elasticity)及黏滯程度(viscosity)。此外，我們亦提出一個新的脈衝式磁致動超音波影像運動追蹤(motion tracking)演算法來降低磁場強度分布不均勻的影響。實驗中我們以5 kHz幀率的超快平面波成像來實現脈衝式磁致動超音波，以其來追蹤在8 ms磁脈衝下所導致超順磁性氧化鐵奈米粒子的振動。實驗確認了在有無加入超順磁性氧化鐵奈米粒子仿體的超快平面波磁致動超音波影像上可以發現有明顯差異。其偵測到的位移量會隨著超順磁性氧化鐵奈米粒子濃度增加而呈現上升趨勢。此外，我們亦製作0.5%、1%及1.5%不同比例瓊脂膠體仿體來仿效不同彈性的組織。在這三組仿體上，可觀察到其超順磁性氧化鐵奈米粒子的動態變化曲線有明顯的差異。整體而言，驗證了我們所提出的超快磁致動超音波影像技術搭配磁脈衝用於觀測超順磁性氧化鐵奈米粒子分布及超順磁性氧化鐵奈米粒子的動態變化情形之可行性。未來將進一步改善運動追蹤的演算法以及更進一步探討組織彈性及黏滯程度和超順磁性氧化鐵奈米粒子動態變化之間的關係。

Recently, pulsed magnetomotive ultrasound (pMMUS) imaging has been introduced to detect superparamagnetic iron oxide nanoparticles (SPIO) which is not able to be visualized by conventional ultrasound. However, because of the used magnetic short pulse, the reported pMMUS only can use a single-element ultrasound transducer along with mechanical scanning to perform imaging, which significantly limits the imaging fame rates. To solve this problem, we propose an ultrafast plane wave imaging based pMMUS technique. The ultrafast frame rate of plane wave imaging is fast enough to track the magneto-motion of the excited SPIOs during the period of the magnetic pulse being applied. Therefore, the proposed ultrafast plane wave pMMUS is capable of visualizing the dynamic response of the excited SPIOs, which is highly correlated to tissue characteristics such as viscosity and elasticity, to an externally-applied magnetic pulse. In addition, a new pMMUS motion tracking algorithm based on ultrafast plane wave imaging is developed to reduce the effect of magnetic field inhomogeneity. In our experiments, ultrafast plane wave imaging with a 5 kHz frame rate was used to implement the pMMUS where the SPIO motion induced by an 8-ms magnetic pulse was tracked. The results showed that there were significant differences between the ultrafast plane wave pMMUS images of the phantoms with and without SPIOs embedded. There was a monotonic increase in displacement with increased concentration of SPIOs. In addition, agarose phantoms with 0.5%, 1% and 1.5% agarose were used to mimic tissues with different elasticity. The dynamic responses of the excited SPIOs in the three types of phantoms were distinguishable. Overall, it is demonstrated that the feasibility of our proposed ultrafast plane wave pMMUS imaging technique for the visualization of the magneto-motion and dynamic response of the SPIOs under the excitation of a short magnetic pulse. More studies are required to further improve the magneto-motion tracking algorithm and explore the relationship between the dynamic response of the excited SPIOs and the tissue viscosity and elasticity.

中文摘要 I
Abstract III
誌謝 IV
目錄 VII
圖目錄 X
第一章 緒論 1
1.1 磁性材料之特性 1
1.2 超順磁性氧化鐵奈米粒子 4
1.2.1 超順磁性氧化鐵奈米粒子生醫上之應用 5
1.2.1.1 超順磁性氧化鐵奈米粒子作為影像對比劑 6
1.2.1.2 熱治療 7
1.2.1.3 藥物遞送 8
1.2.1.4 磁分離 9
1.2.2 超音波監測超順磁性氧化鐵奈米粒子的限制 10
1.3 磁致動超音波影像 11
1.3.1 磁致動超音波影像基本原理 11
1.3.2 磁致動力 13
1.3.3 影響磁致動力參數之探討 15
1.3.4 超音波影像用於偵測組織位移量 16
1.4 研究動機與目的 18
1.5 論文架構 19
第二章 材料與方法 21
2.1 基於超快平面波成像之脈衝式磁致動超音波技術 21
2.1.1 脈衝式磁場 21
2.1.2 超快平面波成像 27
2.1.3 超順磁性氧化鐵奈米粒子製作方式 31
2.1.4 超快平面波磁致動超音波系統及實驗架構 32
2.1.5 實驗資料擷取流程 35
2.1.6 超順磁性氧化鐵奈米粒子之追蹤 37
2.1.7 降低磁場強度不均勻性之演算方法 40
2.1.8 實驗仿體 42
第三章 實驗結果與討論 44
3.1 仿體實驗 44
3.1.1 不同超順磁性氧化鐵奈米粒子濃度仿體的超音波B-mode影像 44
3.1.2 不同超順磁性氧化鐵奈米粒子濃度仿體的超快平面波磁致動超音波影像 45
3.1.3 超順磁性氧化鐵奈米粒子濃度與位移量強度關係 48
3.1.4 不同軟硬度仿體的超音波B-mode影像 49
3.1.5 不同軟硬度仿體的超快平面波磁致動超音波影像 51
3.1.6 仿體彈性係數與位移量大小關係 53
3.1.7 仿體軟硬度超順磁性氧化鐵奈米粒子動態變化曲線關係 54
3.1.8 降低磁場強度不均勻性 56
第四章 結論與未來工作 59
4.1 結論 59
4.2 未來工作 59
參考文獻 62

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