醫用超音波具非侵入式以及即時成像的優點，是臨床廣泛使用的診斷工具。近年來高頻超音波的快速發展，醫用超音波影像由較深組織(如肝臟組織、心臟組織等)，轉移到細微表淺組織評估(如皮膚病變、血管增生)。然而目前高頻超音波的解析度與可視景深要觀察血管增生都尚且不足，故本研究使用以高頻驅動線路與快速多重聚焦影像重建技術，來增加高頻超音波影像解析度及總可視景深範圍。本研究所設計的高頻驅動電路，具有脈衝調變、高功率、以及低成本的優勢，並與市售儀器所使用的單極性脈衝觸發電路做一比較。測試結果方面，本實驗利用50 MHz高頻超音波探頭搭配高速移動平台，可提供以下幾種不同的掃描模式：A-mode、B-mode、C-mode以及多重聚焦掃描，並利用時間增益補償(TGC)來回饋超音波衰減的物理特性，藉此提高組織深處影像對比度。在B-mode即時影像的程式設計，建構了利用參數自動產生馬達控制程式碼功能，減少了使用者操作的複雜度，更可以達到快速影像重建(每秒三張影像)，影像的軸向與橫向長度分別為3.8 mm與6 mm。在多重聚焦影像的校正，本論文提出以影像對位的方法，分別以最小平方差(LSD)、相關係數法(Cross-correlation)，本論文將相關係數法在LabVIEW上實現，在一秒內完成兩張B-mode影像的影像對位。超音波假體掃描的實驗結果指出，快速多重聚焦影像的軸向和橫向解析度分別為 50 μm和100 μm，可視深度為6 mm。結果顯示得到較佳的多重聚焦影像，且大幅增加了影像的可視深度，讓高頻超音波系統提供了更多資訊。

Medical ultrasound is widely used in clinical diagnosis because of noninvasive and real-time imaging. With the rapidly development of high frequency ultrasound in recent years, the research of medical ultrasonic image focuses on superficial tissue. However, the resolution and depth of field (DOF) of the current system are not enough to estimate angiogenesis. This study attempts to build the high frequency driving circuit and uses high speed multi-focus image reconstruction technique to increase the resolution and the total DOF. The high frequency driving circuit was designed using pulse width modulation (PWM) approach with high energy and low cost. In the experiment, the image was reconstructed with the echo signal of the 50 MHz transducer which performed the mechanical scanning by the three dimensional motor platform. There are several available scanning modes could be selected including A-mode, B-mode, C-mode, and multi-focus mode. The automatically generated code for motion controlling is developed in the system. It can reduce the complexity of operation and achieve high speed image reconstruction (3 frames per second). The axial and lateral width of the image is 3.8 mm and 6 mm respectively. We use the cross-correlation method to implement image alignment. From the test of ultrasonic phantom, the axial resolution and lateral resolution are 50 μm and 100 μm respectively in multi-focus image. In addition, the DOF was increased to around 6 mm, raise of 58%. The results indicate that the multi-focus image has higher performance and broader DOF.

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