微氣泡殼層厚度對二次諧振強度的影響

Influence of Shell Thickness on the Second Harmonic Response of Encapsulated Microbubble

曹偉桓(Wei-Huan Chao)

指導教授 ： 曹建和

國立臺灣大學/電機資訊學院/電機工程學研究所/碩士(2006年)

https://doi.org/10.6342/NTU.2006.00949

摘要

欲建構一超音波藥物傳輸系統，藥物載體的攜藥量(dosage)以及藥物釋放劑量(release)的計算為一重要之課題。對於微脂粒，其多層膜之殼層為其包覆藥物之空間。因此，其殼層厚度對攜藥量的計算具有指標性的意義。然而目前尚無非破壞性的方法來評估微脂粒的殼層厚度，於本研究中，我們將自行製備微脂粒，且藉由C.C. Church之帶殼微氣泡動力學理論，模擬其散射訊號，並且藉由實驗比對數值模擬之結果。數值模擬的結果顯示對於相同大小的微脂粒，厚度越薄，其二次諧振的強度越強；於實驗，針對殼層厚度為17.5奈米的微脂粒以及厚度為3.5奈米的微脂粒兩種樣品的散射訊號相比較，兩者的基頻強度無太大差異，但其二次諧振的強度差約6dB，此實驗結果與數值模擬的趨勢相同；此研究結果在未來有潛力可用來評估帶殼微氣泡之殼層厚度，進而計算藥物載體之攜藥量。

關鍵字

微氣泡

並列摘要

For ultrasound drug delivery applications, dosage prediction before release and estimation after release are required functions. Liposome can be used as a drug carrier and encapsulate drug in its shell. Therefore it has great value to evaluate shell thickness.
However, there is no appropriate invasive method to determine the shell thickness of multi lamellar liposome. In this study , We make liposomes consisting of gas for experimental test. we use the Church’s model with parameter of phospholipids bilayers to simulate the frequency responses of the backscattered signal and establish an experimental protocol to compare with the simulated result.
From simulation, it is shown that thinner layers will increase the second harmonic response. The shell thickness of liposome is controlled by sonicator which can diminish the numbers of layers. To test the liposomes with different shell thickness, pulse trains (PRF=1KHz , B.W=5%) are transmitted with center frequencies at 2MHz and 1.75MHz, then backscattered signals are received and digitized for processing. For the 1.75 MHz and 2MHz experiment, referred to the echo of liposomes with 3 to 5 layers, the second harmonic response generated by liposomes with 1 to 2 layers is about 6 dB higher. The trends of signal dependence on the thickness and center frequency agree with the simulation studies. A potential application of this study is to evaluate the shell thickness and dosage of liposomes further.

並列關鍵字

microbubble

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