臺灣博碩士論文加值系統

超音波影像（ultrasonic imaging）因為有低成本、非侵入性（non-invasiveness）、即時成像、與儀器較方便攜帶等優點，所以是一種被廣泛使用的造影方式。隨著VLSI及製程技術的演進，可攜式超音波影像系統在近十幾年來逐漸成為重要的趨勢，讓醫師可在不需移動病患的情況下立即診治，提升病患就診的方便性也降低病患的痛苦；除此之外，可攜式系統在緊急救護上更扮演著不可或缺的重要角色，大幅度的提升存活率。
彩色都卜勒影像為超音波影像系統中重要的成像模式之一，可即時地將人體內血液分佈及流速快慢變化呈現在二維影像上，提供臨床診斷及治療。但傳統彩色都卜勒影像容易受到體內組織運動、呼吸、脈搏跳動等受測者與探頭間相對運動影響，些許的相對運動就會降低影像品質以及血流相關參數的準確度。因此在一般情況下，受測者必需在短時間內緊閉呼吸以降低相對運動的產生，然而當其應用在急診室、開刀房和救護車等緊急救護的情況下以及年齡過小的孩童身上，很難避免受測者與超音波探頭之間的相對運動，而使得影像品質低落，以致醫師難以進行診斷。除了相對運動外，參數設定也是彩色都卜勒一大課題。傳統彩色都卜勒引擎需要複雜的參數設定，難以在變化的環境下適當調整參數即時成像。尤其在緊急救護上，複雜的參數設定更是一大阻礙。
本論文的研究主題是設計並實現一智慧型彩色都卜勒的數位訊號處理引擎（Intelligent color Doppler DSP engine）。此超音波系統的目標有三，分別為良好的影像品質、智慧型及高攜帶性。首先，本設計發展一套適用於彩色都卜勒去除相對運動造成運動假象(motion artifact)的機制，提升影像品質。其次，本設計採用可適性演算法降低雜訊，簡化參數設定，使各式濾波器能智慧地自動根據環境的變化做調整。最後，本設計是由特製化的專用積體電路（application-specific integrated circuit, ASIC）作實現，相較於目前一般處理器的架構而言，能大大地減少成本與功率的消耗。

Ultrasonic imaging is a well-established imaging modality that has the advantages of cost-effectiveness, non-invasiveness, rapid imaging, and portability. With the progress of VLSI technique, portable ultrasound imaging systems have become a trend for tens of years. They are easily carried to where patients are, which largely decrease the inconvenience and pain for patients. Moreover, portable systems become more indispensable in supporting immediate diagnosis for emergency rescue to increases the survival rate.
Color Doppler imaging, one of the Doppler ultrasound modes, is valuable for visualizing the distribution and velocity by different colors in real time. However, traditional color Doppler imaging suffers from the motion between the probe and the patients. Slight motion causes severe image corruption. Although patients are asked to hold their breath and stay steady, motion cannot be avoided for child subject or in emergency situation such as ambulance, emergency room, and in battlefield. Furthermore, traditional Doppler engine needs complex parameter settings, which brings inconvenient and time-consuming adjustment. It also leads to large operation area reducing the portability of the ultrasound imaging system.
In this thesis, the research topic is to design and implement an intelligent color Doppler DSP engine for the portable ultrasonic imaging system. The major goals of the color Doppler DSP engine are high image quality, intelligent property, and portability. Hence, the presented engine is guided to have three features. First, it possesses an effective mechanism to eliminate motion artifact to reach good image quality. Second, it is designed with intelligent consideration, which eliminating noises adaptively with environment by easy parameter settings. Finally, it is implemented with customized ASIC design for low power and low cost considerations.

Contents
致謝 v
摘要 vii
Abstract ix
Contents xi
List of Figures xiii
List of Tables xvi
Chapter 1 Introduction 1
1.1 Overview of Portable Ultrasonic Imaging Systems 1
1.2 Research Topics and Main Contributions 4
1.3 Thesis Organization 7
Chapter 2 Portable Ultrasonic Imaging Systems 8
2.1 System Description 8
2.2 Doppler Ultrasound Basics 10
2.3 Color Doppler DSP Engine 14
Chapter 3 Proposed Velocity Bias Cancellation Algorithm 24
3.1 Motion Artifact in Color Doppler 24
3.2 Proposed Velocity Bias Cancellation Algorithm 26
3.3 Simulation Environment 32
3.4 Performance Evaluation 33
3.5 Summary 39
Chapter 4 Intelligent setting of Key DSP Modules 40
4.1 Adaptive Energy Thresholding 40
4.2 Simulation Results of Adaptive Energy Thresholding 42
4.3 Modified Adaptive-size Median Filter 44
4.4 Simulation Results of Adaptive-size Median Filter 46
4.5 Summary 48
Chapter 5 Architecture Design and VLSI Implementation 50
5.1 Overall system and parameter specification 50
5.2 Architecture Design of Color Doppler DSP Engine 51
5.3 VLSI Implementation and Summary 61
Chapter 6 Conclusion 64
6.1 Main Contribution 64
6.2 Future Direction 65
References 66

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