同調平面波複合成像在超音波成像中漸漸扮演重要的腳色，藉由發射多角度的平面波，同調平面波複合成像可以提供超快超音波成像與彈性影像。在本研究中，我們針對同調平面波複合成像提出了一個角度挑選策略，在發射較少平面波的情況下，我們提出的方法與常用的角度序列 – 等角度間距間隔抽取 (EAS-CPWC) 相比，可以達到較少的柵瓣與假影。在我們的策略中，首先找出傳統的合成孔徑成像與同調平面波複合成像的關係。透過我們的角度挑選策略，在給定發射的平面波最大角度後，同調平面波複合成像的等效合成孔徑會近似期望的雙向等效孔徑，並且具備適當的等效孔徑寬度、探頭間距與等效孔徑形狀，因此可以抑制柵瓣與假影。我們藉由超音波模擬(Field II)線仿體、消聲囊腫仿體與離體豬動脈來驗證我們的角度挑選策略。模擬與實驗結果顯示柵瓣與假影可分別抑制5 dB 與15 dB，而對比雜訊比可達到25± 5 % 的改進。整體上來說，我們證明了本篇論文所提出的角度挑選策略可以有效地抑制柵瓣與假影。

Recently, ultrasound imaging with coherent plane wave compounding has played an important role in high-quality ultrafast imaging and shear wave elastography, leveraging multiple angled plane-wave emissions. In this study, we propose an angle selection strategy for ultrasound imaging with coherent plane wave compounding (CPWC), featuring lower grating-lobe and ghost artifacts while fewer angled plane-wave emissions are required compared to commonly used equal-angular-spacing decimation in the angle sequence (EAS-CPWC). In our strategy, the relation between conventional synthetic transmit aperture imaging and CPWC is discovered. Given the number of the total tilted plane-wave excitations, with our angle selection strategy, the synthesized effective aperture by the CPWC approximates to the desired two-way effective aperture with an appropriate width, element spacing, and shape; thus enabling grating-lobe and ghost artifacts suppression. Field II simulations and experiments on wire, anechoic cyst phantoms and the ex vivo porcine artery were performed to verify our angle-selection strategy. Simulation and experimental results showed that with our proposed angle sequence, the grating-lobe and ghost artifacts were suppressed by 5 dB and 15 dB respectively, and 25 ± 5 % contrast-to noise ratio (CNR) improvement was achieved. Overall, we demonstrated the efficacy of our proposed angle sequence for grating-lobe and ghost artifacts suppression.

中文摘要 I
Abstract II
Contents III
List of Figures V
List of Tables IX
Chapter 1 Introduction 1
1.1 Coherent Plane Wave Based Ultrasound Imaging Using Linear Array 1
1.2 Artifacts of Sparse Coherent Plane Wave Compounding 3
1.2.1 Beam Pattern of a Linear Array 3
1.2.2 Ghost Artifact 5
1.2.3 Grating-Lobe Artifact 7
1.3 Artifacts Suppression 9
1.4 Motivation 11
1.5 Organization of the Thesis 12
Chapter 2 Materials and Methods 13
2.1 Relationship Between Transmit Elements and Plane-Wave Steering Angles under Continuous Wave Assumption 13
2.2 Strategy for Sparse Angle Selection 16
Chapter 3 Results and Discussion 21
3.1 Simulations 22
3.1.1 Single Point Target 22
3.1.2 Fully Developed Speckle Background 25
3.1.3 Multiple Point Targets 27
3.1.4 Cyst Phantom 29
3.2 Experiments 31
3.2.1 Single Point Target 31
3.2.2 Multiple Point Targets 33
3.2.3 Cyst Phantom 35
3.2.4 Ex Vivo Porcine Aorta 37
Chapter 4 Conclusions and Future Work 40
4.1 Conclusions 40
4.2 Future Work 41
References 42

[1] G. Ronaldo, M. Tranter, J. Bercoff, N. Benech, and M. Fink, “Coherent plane-wave compounding for very high frame rate ultrasonography and transient elastography,” IEEE Trans. Ultrason., Ferroelectr., Freq.Control, vol. 56, no. 3, pp. 489–506, Mar. 2009.
[2] A. Rodriguez-Molares, Hans Torp, Bastien Denarie,and Lasse Lovstakken, “The Angular Apodization in Coherent Plane-Wave Compounding,” IEEE Trans. Ultrason., Ferroelectr., Freq.Control, vol. 62, no. 11, pp. 2018–2023, Nov. 2015.
[3] A. Macovski, “Ultrasonic Imaging Using Arrays,” Proc. of IEEE, vol. 67, no. 4, pp. 484-495, Apr. 1979.
[4] A. Rodriguez-Molares, J. Avdal, H. Torp and Lasse Lovstakken, “Axial lobes in Coherent Plane-Wave Compounding,” Proc. IEEE Int. Ultrason. Symp., Sep. 2016.
[5] J. Jensen, M. B. Stuart, and J. A. Jensen, “Optimized Plane Wave Imaging for Fast and High-Quality Ultrasound Imaging,” IEEE Trans. Ultrason., Ferroelectr., Freq.Control, vol. 63, no. 11, pp. 1922–1934, Nov. 2016.
[6] B. Denarie, T. A. Tangen, I. K. Ekroll, N. Rolim, H. Torp, T. Bjastad and L. Lovstakken, “Coherent Plane Wave Compounding for Very High Frame Rate Ultrasonography of Rapidly Moving Targets,” IEEE Trans. Medical Imaging, vol. 32, no. 7, pp.1265-1276, Jul. 2013.
[7] Y. Zhang, Y. Guo and Wei-Ning Lee, “Ultrafast Ultrasound Imaging Using Combined Transmissions With Cross-Coherence-Based Reconstruction,” IEEE Trans. Medical Imaging, vol. 37, no. 2, pp. 337-348, Feb. 2018.
[8] G. R. Lockwood, Pai-Chi Li, M. O’Donnel, and F. Stuart Foster, “Optimizing the Radiation Pattern of Sparse Periodic Linear Arrays,” IEEE Trans. Ultrason., Ferroelectr., Freq.Control, vol. 43, no. 1, pp. 7–14, Jan. 1996.
[9] H. Liebgott, A. Rodriguez-Molares, F. Cervenansky, J.A. Jensen and O. Bernard, “Plane-Wave Imaging Challenge in Medical Ultrasound”.
[10] Laurent S, Saei AA, Behzadi S, Panahifar A, Mahmoudi M. Superparamagnetic iron oxide nanoparticles for delivery of therapeutic agents: opportunities and challenges. Expert opinion on drug delivery 2014;11(9):1449-70.