MULTIFREQUENCY ULTRASOUND RADIATION FORCE EXCITATION AND MOTION DETECTION OF HARMONICALLY VIBRATING SCATTERERS A THESIS SUBMITTED TO THE FACULTY OF THE MAYO CLINIC COLLEGE OF MEDICINE MAYO GRADUATE SCHOOL BY MATTHEW W. URBAN IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN BIOMEDICAL SCIENCES- BIOMEDICAL ENGINEERING Acknowledgments There are many people that I would like to thank for their contributions to this work and making my time at Mayo fruitful. I would like to extend my gratitude to my advisor, Dr. James F. Greenleaf for his guidance throughout this research project. I would also like to thank my committee members for their assistance with this thesis work: Dr. Mostafa Fatemi, Dr. Armando Manduca, Dr. Stephen J. Riederer, Dr. Kai-Nan An, and Dr. Hal H. Ottesen. The Ultrasound Research Laboratory has been instrumental in the successful completion of this work. I am indebted to Randy Kinnick for the substantial contributions that he made in helping me with experiments and Tom Kinter for writing software to perform my experiments. I would like to thank Elaine Quarve and Jennifer Milliken for their secretarial assistance. I also would like to acknowledge Dr. Shigao Chen, Dr. Glauber Silva, Dr. Farid Mitri, Dr. Xiaoming Zhang, Dr. Azra Alizad, Dr. Yi Zheng, Dr. Thomas Huber, and Miguel Bernal for their scientific input to my research. I would like to thank my fellow students Heather Argadine, Mambi Madzivire, and Carrie Hruska for making this time at Mayo an enjoyable experience. Lastly, but surely not least, I would like to extend my deepest gratitude to my family for their love and support throughout my education. My mother and father have been instrumental in providing loving encouragement throughout my schooling. I want to thank my wife Joleen for all love and support I could ask for and for the sacrifices that she made to allow me to pursue my education. I dedicate this work to my wife Joleen and my daughter Lily as they have been the source of inspiration to complete this work. ii Contents List of Figures................................................................................................................... vi List of Tables ................................................................................................................xviii Chapter 1—Introduction.................................................................................................. 1 1.1 Background ............................................................................................................ 1 1.2 Elasticity.................................................................................................................. 2 1.3 Viscoelasticity ......................................................................................................... 5 1.4 Elasticity Imaging .................................................................................................. 6 1.5 Force Excitation ..................................................................................................... 7 1.5.1 External Excitation Sources........................................................................... 7 1.5.2 Internal Excitation Sources............................................................................ 8 1.5.3 Endogenous Excitation Sources................................................................... 10 1.6 Measurement of Deformation............................................................................. 10 1.6.1 Magnetic Resonance Imaging ...................................................................... 10 1.6.2 Ultrasound Imaging...................................................................................... 11 1.6.3 Optical Signals............................................................................................... 13 1.6.4 Acoustic Signals............................................................................................. 13 1.7 Vibro-acoustography ........................................................................................... 13 1.8 Thesis Description................................................................................................ 17 Chapter 2—Measuring the Phase of Vibration of Spheres in a Viscoelastic Medium as an Image Contrast Modality ..................................................................................... 20 2.1 Introduction........................................................................................................... 20 2.2 Methods.................................................................................................................. 23 2.2.1 Dynamic Motion of a Sphere ........................................................................ 23 2.2.2 Phase of Vibration......................................................................................... 24 2.3 Experiment ............................................................................................................ 30 2.3.1 Experimental Setup ....................................................................................... 30 2.3.2 Experimental Results..................................................................................... 32 2.4 Discussion.............................................................................................................. 36 2.5 Conclusion ............................................................................................................ 39 Chapter 3—Multifrequency Vibro-acoustography and Vibrometry......................... 40 3.1 Introduction.......................................................................................................... 40 3.2 Multifrequency Radiation Stress........................................................................ 43 3.3 Multifrequency Implementation......................................................................... 45 3.4 Point-spread Function Calculations................................................................... 49 3.5 Image Formation.................................................................................................. 50 3.6 Signal-to-Noise Ratio Analysis............................................................................ 51 3.6.1 Dynamic Radiation Force and its Effects ................................................... 52 3.6.2 Multifrequency Vibro-acoustography ........................................................ 53 3.6.3 Signal-to-Noise (SNR) Ratio Analysis ......................................................... 54 3.6.4 Chirp Multifrequency Implementation ...................................................... 55 3.7 Multifrequency Experiments .............................................................................. 56 iii 3.7.1 Point-spread Function Simulation............................................................... 56 3.7.2 Point-spread Function Experimental Validation....................................... 56 3.7.3 Vibrometry Experiment ............................................................................... 58 3.7.4 Vibro-acoustography Experiment............................................................... 58 3.7.5 In Vivo Breast Imaging................................................................................. 59 3.8 Multifrequency Experimental Results ............................................................... 60 3.9 Discussion.............................................................................................................. 69 3.10 Conclusion .......................................................................................................... 76 Chapter 4—Harmonic Motion Detection of a Vibrating Reflective Target.............. 77 4.1 Introduction.......................................................................................................... 77 4.2 Theory ................................................................................................................... 79 4.3 Parameterized Model........................................................................................... 82 4.4 Parameterized Model Results ............................................................................. 86 4.5 Discussion.............................................................................................................. 92 4.6 Conclusion ............................................................................................................ 95 Chapter 5—Harmonic Pulsed Excitation and Experimental Motion Detection of a Vibrating Reflective Target ........................................................................................... 96 5.1 Introduction.......................................................................................................... 96 5.2 Background .......................................................................................................... 96 5.3 Harmonic Pulsed Excitation ............................................................................... 98 5.3.1 Harmonic Pulsed Excitation Experiment ................................................. 101 5.3.2 Harmonic Pulsed Excitation Experimental Results................................. 103 5.4 Motion Detection Experiment........................................................................... 104 5.4.1 Parameter Analysis..................................................................................... 111 5.5 Motion Detection Experimental Results 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