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系統識別號 U0026-2008201113170300
論文名稱(中文) 建構一套高頻超音波影像系統
論文名稱(英文) Development of a High Frequency Ultrasonic Imaging System
校院名稱 成功大學
系所名稱(中) 醫學工程研究所碩博士班
系所名稱(英) Institute of Biomedical Engineering
學年度 99
學期 2
出版年 100
研究生(中文) 陳明杰
研究生(英文) Ming-Jay Chen
學號 p86981075
學位類別 碩士
語文別 英文
論文頁數 47頁
口試委員 指導教授-陳天送
口試委員-陳家進
口試委員-姚維仁
口試委員-陳培展
口試委員-陳世中
中文關鍵字 高頻超音波  時間增益補償  多重聚焦掃描 
英文關鍵字 high-frequency ultrasound  time gain compensation (TGC)  Multi-Focus scans 
學科別分類
中文摘要 醫用超音波是一項非侵入式且安全的臨床診斷工具,當使用超音波影像來觀測微小組織時,最重要的莫過於解析度了。較高頻率的超音波可以提供較高的影像解析度,但不適用於深層組織之觀察,其臨床應用主要於體表淺層的組織或微小特定區域。此外,現今的高頻超音波陣列探頭其製造仍有一定的困難性,這也導致售價較一般頻段的超音波探頭來的昂貴。有鑑於此,本研究利用單一顆20 MHz超音波探頭搭配高速移動平台,建立一套高頻超音波影像系統,此系統可以提供以下幾種不同的掃描模式,包含A-mode、B-mode、C-mode以及多重聚焦掃描。在超音波影像系統中,時間增益補償(TGC)可以有效調整超音波訊號強度,藉此提高影像對比度,常見於傳統B-mode影像的使用;多重聚焦的掃瞄方式是透過不同Z軸高度取得相對的聚焦影像,最後整合成一張最終成像,這樣的成像方式使用傳統的時間增益補償常因過度增益而造成假影和邊界削弱等現象,特別在無回聲的區域中,本研究提出自調整的增益模式來解決此問題。在實驗結果方面,我們使用硬幣及超音波假體來驗證系統的性能。所使用的硬幣假體大小為20*20 mm,以C-scan模式進行弓形的掃描;影像結果顯示該系統的橫向和縱向解析度分別為59 μm和123 μm,成像效果相當好。超音波假體的實驗結果指出,B-mode影像的軸向和橫向解析度分別為 57 μm和136 μm,可視景深為2.016 mm;在多重聚焦的掃描結果下也顯示影像品質明顯的提升,並大幅抑制波形發散的現像。最後在有無使用時間增益補償方法的B-mode與多重聚焦影像的影像結果比較中得知,使用時間增益補償的方法可提供比原始影像更好的對比效果。
英文摘要 Medical ultrasound technique is a safe and noninvasive tool for clinical diagnosis or prognosis on tissue evaluation. The resolution of ultrasonic image is important especially in observing small tissues. High-frequency ultrasound could provide high-resolution image, but it would reduce the monitoring depth of tissue. However, it is useful for special clinical application, especially in superficial tissue. Currently, high frequency ultrasound array is still very difficult to implement and high manufacturing cost. In order to overcome these problems, the purpose of this study is to design a high frequency ultrasound system that utilized a single 20 MHz ultrasonic transducer with high speed towing platform to achieve imaging function. The proposed system had several scan modes including A-mode, B-mode, C-mode and Multi-Focus scan mode. Time gain compensation (TGC) is provided on an automatic basis by storing an amplification gain function to adjust received ultrasonic signals. Moreover, multi-focus technique based on single transducer usually combines with plurality of individual zones of image, and image vertical resolution and intensity could improve from different z-axis. However, most of the automatic TGC used in ultrasound scanners induces artifacts and weakens the edges because of over-gains, especially in the anechoic regions of multi-focus images. Two phantom experiments with coin and ultrasonic phantom were designed to verify the performance of purposed system. In coin experiment, we used a coin phantom (20*20mm) for ultrasound C-scan mode. The scan trajectory was similar to bow-shaped scan and the result image showed that the system transverse and vertical resolutions were 59μm and 123μm, respectively. The results of ultrasonic phantom (N-365 Multipurpose Phantom) indicated that axial and lateral resolution of B-mode image was 57 and 136 μm, respectively and depth of field was 2.016 mm. In addition, multi-focus scan could improve image quality efficiently through decreasing the effect of divergence in ultrasonic waveform. Comparing the results of B-mode and Multi-Focus scan images with/without our TGC method, image with TGC method could provide better contrast in different tissue types than the original one.
論文目次 摘要 I
Abstract II
誌謝 III
Chapter 1 Introduction 1
1.1 Background 1
1.1.1 Development and application of ultrasound 1
1.2 Motivation and Objectives 3
1.3 Literatures Review 3
1.3.1 System Construction 3
1.3.2 System Applications 5
Chapter 2 Materials and Methods 7
2.1 System Description 7
2.2 System Design 9
2.2.1 Motion Control System 10
2.2.2 Trigger control circuitry 11
2.2.3 Fixture design 12
2.2.4 System flowchart 13
2.3 Equipments Overview 16
2.3.1 Transducer 16
2.3.2 Linear servo motor (HR8) 19
2.3.3 Motion card 20
2.3.4 Pulser-Receiver 21
2.3.5 High-Speed Digitizers 22
2.4 Measurement mode 22
2.4.1 Reflection Mode 23
2.4.2 Transmission Mode 23
2.5 Scan mode 23
2.5.1 A-mode 23
2.5.2 B-mode 24
2.5.3 C-mode 24
2.5.4 Multi-Focus scans 25
2.6 Hilbert Transform 25
2.7 Time Gain Compensation (TGC) 26
2.8 Design of Experiments 27
2.8.1 Experimental І - Scan platform performance testing 27
2.8.2 Experimental ІІ - Imaging system calibration 29
2.8.3 Experimental ІІІ - C-mode scanning experiment (coin) 30
2.8.4 Experimental ІV - Hand vascular experiment (B-mode) 31
Chapter 3 Results and Discussions 32
3.1 Scan platform performance testing 32
3.2 System Calibration 34
3.2.1 B-mode Scan 34
3.2.2 Multi-Focus Scan 36
3.2.3 Time Gain Compensation (TGC) 38
3.3 C-mode Scan 41
3.4 Hand vascular experiment ( B-mode) 41
Chapter 4 Conclusions 44
References 46
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