臺灣博碩士論文加值系統

在近年來的研究中，聚焦式超音波已被證實可做局部且具回復性之血腦屏障暫開功能，因此有潛力將大分子藥物送入腦組織以進行局部藥物釋放及治療。目前可用的系統設計中其頻率都大於500kHz，目的都是為了達到聚焦效果來作熱燒灼治療。然而使用500kHz以上頻率聚焦時，其能量將會被完整的頭骨所阻礙吸收。本研究之目的在於設計一套用64通道之低頻超音波相位陣列系統用來產生血腦屏障暫開功能。本系統包含了以FPGA/微處理器為主的控制核心、64通道功率可調之驅動模組、多通道功率偵測模組，以及48通道之半球型超音波相位陣列換能器。此設計方式由數位電路產生多通道之相差訊號，並經過功率放大器後輸出至超音波相位陣列之每一陣元上，使半球型設計的超音波換能器能在空間上產生一聚焦點，透過相差訊號的改變，可以將超音波能量聚焦於特定位置。於系統性能測試上，包含輸出功率測試、功率回授測試、聲壓力值以及聲壓力分佈量測等。實驗結果顯示可成功利用本系統達到良好聚焦能力以及改變相位來控制焦點位置並顯示功率在介面上。

Focused ultrasound has been proven to have potential for local and reversible blood-brain barrier disruption in recent years, thereby contains potential for macromolecular drugs delivery into brain tissue to perform targeting brain drug delivery for brain disorder treatment. Current available system all design frequency higher than 500 kHz in order to generate focus for ultrasonic thermal ablation purpose. However, operating frequency higher than 500 kHz encounters obstacle that the energy could be blocked by intact skull. The purpose of this study is to design one 64-channel ultrasound phased array system which operates at low frequency for blood-brain barrier disruption. The system include Field Programmable Gate Array (FPGA)/ Micro-controller based control kernel, 64-channel power-controlled driving module, multiple-channel power sensoring module, and one 48-channel hemispherical ultrasound phased array transducer. The novelty of the proposed design is that we proposed to employ the microcontroller unit and the field programmable gate array to serve as the main control unit for multiple channel signals. System performance testing includes output power testing, feedback power testing, acoustic pressure testing and ultrasound pressure measurements. Our results showed that the system can successfully generate ultrasonic focus, and the focal position can be scanned by controlling the relative phases of elements with output power monitoring.

目錄
誌謝......................................................V
摘要.....................................................VI
ABSTRACT................................................VII
目錄...................................................VIII
圖目錄...................................................XI
表目錄..................................................XIV
第一章 緒論................................................1
1-1 前言..................................................1
1-2 研究動機與目的..........................................2
1-3 論文架構...............................................3
第二章 超音波系統基本理論....................................4
2-1 半橋切換式轉換器........................................4
2-2 阻抗匹配概念原理........................................8
2-3.1 最大功率轉移.........................................9
2-3.2 駐波比定義與史密斯圖的應用............................11
2-3 定向耦合器............................................13
2-4 壓電陶瓷..............................................14
2-4.1 正逆壓電效應與壓電方程式..............................15
2-4.2 等效電路............................................19
2-4.3旁波瓣與衍生瓣.......................................20
第三章 驅動電路設計........................................22
3-1 數位系統控制電路.......................................23
3-1.1 正反器串聯相位產生...................................23
3-1.2 FPGA整合相位產生....................................25
3-1.3 數位控制中樞........................................26
3-1.4 Buffer緩衝電路......................................27
3-1.5 GUI控制介面設計.....................................27
3-2 類比系統放大電路.......................................28
3-2.1 波寬調變延遲電路.....................................28
3-2.2 半橋式功率放大電路...................................30
3-2.3 匹配電路設計........................................32
第四章相位陣列之功率回授及校正系統...........................33
4-1 半球頭罩式換能器.......................................33
4-1.1 換能器製作..........................................33
4-1.2 阻抗匹配...........................................35
4-2 功率回授系統..........................................36
4-2.1 雙定向耦合器........................................36
4-2.2 多通道切換式功率量測.................................38
4-3 相位校正聲場量測系統...................................39
4-3.1 相位校正............................................40
4-3.2 三軸定位聲場量測平台.................................41
第五章 系統整合測試與實驗結果...............................45
5-1 數位控制中樞相位偏移解析度..............................45
5-2 類比放大器輸出能力.....................................46
5-2-1單通道功率及轉換效率測試...............................46
5-2-2 多通道放大器效能測試.................................46
5-3 阻抗匹配對輸出功率影響.................................49
5-4 壓電元件頻率與效率之關係................................50
5-5 校正前後超音波換能器二維聲場壓力圖.......................51
5-6 電子式聚焦點偏移二維聲場壓力圖..........................54
第六章 結論與未來研究方向...................................61
6-1 結論.................................................61
6-2未來研究方向...........................................62
參考文獻..................................................64
圖目錄
圖2-1、簡易型半橋切換式換流器架構............................4
圗2-2、(a) 第一狀態........................................6
圗2-2、(b) 第二狀態........................................6
圗2-2、(c) 第三狀態........................................7
圗2-2、(d) 第四狀態........................................7
圖2-3、阻抗匹配示意圖.......................................9
圖2-4、最大功率轉移等效電路(a)純電阻 (b)非純電阻..............10
圖2-5、史密斯圖...........................................12
圖2-6、Directional coupler...............................14
圖2-7、未施於應力..........................................16
圖2-8、壓電效應示意圖 (a)正壓電效應 (b)逆壓電效應.............16
圖2-9、壓電陶瓷等效電路模型.................................19
圖2-10、頻率對阻抗與相位增益圖..............................20
圖2-11、Main Beam與side lobe..............................21
圖2-12、Grating lobe.....................................21
圖3-1、超音波相位陣列系統架構...............................22
圖3-2、八級D-FF正反器串接架構...............................23
圖3-3、D-FF正反器串聯相位輸出波形圖.........................24
圖3-4、相位偏移架構圖......................................25
圖3-5、單晶片及FPGA整合系統架構圖...........................26
圖3-6、GUI控制介面........................................28
圖3-7、波寬調變延遲電路....................................29
圖3-8、具有失效時間的切換訊號...............................30
圖3-9、換能器設計架構......................................31
圖3-10、功率放大器.........................................31
圖3-11、阻抗匹配概念圖.....................................32
圖4-1、壓電陶瓷 (a)外觀 (b)阻抗值...........................34
圖4-2、半球頭罩式換能器....................................35
圖4-3、Dual directional coupler..........................36
圖4-4、功率和電壓駐波比轉換公式.............................37
圖4-5、VSWR示意圖.........................................38
圖4-6、切換式功率量測裝測底板設計............................39
圖4-7、量測系統架構圖......................................40
圖4-8、相位校正流程........................................41
圖4-9、(a)三軸平台架構圖 (b)三軸平台GUI介面..................42
圖4-10、行徑路線方式.......................................43
圖4-11、步進馬達控制(a) 步進馬達系統 (b) 順時針轉動時序 (c)逆時針轉動時序..................................................44
圖5-1、(a) 0°同相位輸出 (b)相差90°輸出......................45
圖5-2、(a)電功率與聲功率 (b)壓電片轉換效率...................46
圖5-3、(a)48通道輸出功率 (b)輸出功率平均值...................48
圖5-4、(a)XY軸未校正聲場圖 (b)XZ軸未校正聲場圖...............52
圖5-5、(a)XY軸校正後聲場圖 (b)XZ軸校正後聲場圖...............53
圖5-6、二維聲場壓力圖......................................59
圖5-7、偏移後校正角度......................................60
表目錄
表2-1、 壓電陶瓷狀態方程式..................................18
表3-1、D-FF的輸入頻率所產生之相位差關係......................24
表4-1、 壓電陶瓷規格.......................................33
表5-1、阻抗匹配對功率影響...................................50
表5-2、壓電陶瓷轉換效率及頻寬...............................51

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