中文摘要

　　高頻超音波影像有良好的解析度，且具有非侵入的造影特性而被應用在分子影像和小動物實驗等的研究上，但商用超音波影像系統大多規格固定，應用範圍受到限制，同時提供的功能有限，為了因應實驗室在小動物實驗、編碼波形和聲學應用等多種研究項目，本研究建構一套高頻超音波影像系統，設計資料處理功能以提供實驗時的即時影像觀察，並模組化設計使系統可調整因應不同研究項目的應用需求。
　　本研究使用單一高頻超音波探頭配合馬達系統運動設定，可進行動態掃描、亮度掃描和掃掠掃描等多種運作模式，同時設計系統控制程式讓使用者透過操作介面控制系統進行自動化掃描，此外亦設計動態參數和資料處理程式提供使用者灰階解調影像和流速影像等即時影像的運作選擇，並在整合後測試和調整系統，以同步設計消除擷取訊號的顫動現象、使用電路元件和工作時脈調整抑制系統雜訊、改進馬達與掃描硬體平行運作以及系統控制和資料處理平行處理以提高影像系統整體效能。
　　最後以斑馬魚以及手指靜脈進行系統運作測試，使用40 MHz、3 cycles且聲壓為500 kPa的激發波形，在高速亮度模式運作下可即時輸出每秒30張2 mm × 3 mm的解調影像，穿透深度2 mm的超音波聚焦位置處訊號雜訊比約35 dB；在PRF為4 kHz的動態模式觀察下斑馬魚每分鐘心跳約157次；在PRF為1 kHz的掃掠模式中計算手指靜脈血流速度分量約1 mm/sec。在未來的發展中可加入多重深度的亮度模式增加掃描景深，建立後端資料分析系統提供精確影像分析資訊，以期能更進一步地應用在相關研究領域。

關鍵詞 : 高頻超音波、影像掃描系統、即時影像

Abstract

High-frequency ultrasound provides better imaging resolutions and noninvasive imaging tool for small animal studies. However, most commercial ultrasound imaging systems are designed for specific applications with fixed modules and the utility imaging functions are thus limited. In this study a high-frequency ultrasound imaging system with real-time imaging process was established for the applications in small animal studies.
In system design, one high-frequency ultrasound transducer was mounted on mechanical system. The scanning modes in the system include motion, brightness and swept-scan modes. The user interface provides the connections of control process for automatic operation and data processing function for real-time image display. The design of system synchronous clock eliminated the jitter problem in data acquisition. In addition, the Schottky diode circuits were used to reduce system interference between components. The parallel process in control design of hardware operations and software process improved the performance of the imaging system.
In system performance test, 3-cycles, 40-MHz pulse wave, with an acoustic pressure of 500 kPa, were used to scan the heart of zebrafish and human finger’s vein. The frame rate was up to 30 FPS (2 mm × 3 mm) in B-mode status. In zebrafish image, we can estimate the heart rate of 157 beats/min from our motion mode image with a PRF 4 kHz. The finger’s vein experiment by using swept-scan mode with 1 kHz PRF can estimate the blood velocity ranging from 1 to 10 mm/s. In addition, the development of brightness-depth scan mode and back-end analysis system might be able provide larger DOF and precise image in the future.

Key words: High-frequency ultrasound, Imaging system, Real-time image

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