Multi-scale Quantitative Elastography and its Application to Blood Pressure Estimation Aaron ...

119 Pages·2014·15.19 MB·English

Multi-scale Quantitative Elastography and its
Application to Blood Pressure Estimation
by
MASSACHUSETTS INSiTMTE
OF TECHNOLOGY
Aaron Michael Zakrzewski
B.S., University of Rochester (2011)
IBRARIES
Submitted to the Department of Mechanical Engineering
in partial fulfillment of the requirements for the degree of
Master of Science in Mechanical Engineering
at the
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
September 2013
© Massachusetts Institute of Technology 2013. All rights reserved.
A uthor.............................................
Depart ent of Mechanical Engineering
I-Alugust 0, 203
il
Certified
Brian W. Anthony
Research Scientist
Thesis Supervisor
Accepted by ...... ...................
David E. Hardt
Chairman, Department Committee on Graduate Theses
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Multi-scale Quantitative Elastography and its Application to
Blood Pressure Estimation
by
Aaron Michael Zakrzewski
Submitted to the Department of Mechanical Engineering
on August 8, 2013, in partial fulfillment of the
requirements for the degree of
Master of Science in Mechanical Engineering
Abstract
Elastography is a method that can be used to measure the elasticity of soft biolog-
ical tissue and, ultimately, to detect cancerous tumors. In this thesis, quantitative
compression based ultrasound elastography is developed using a fast multi-scale ap-
proach. The inverse problem optimization methods of elastography are applied to
estimate noninvasively the arterial wall stiffness of a vessel as well as blood pressure.
Simulation and experimental results are presented that predict the accuracy of the
methods. A method is also introduced to eliminate the need for a reference pressure
during the optimization over blood pressure. Using ultrasound, these techniques could
provide noninvasive continuous measurement of blood pressure in major arteries and
could give doctors another way to gather information about a patients cardiovascular
health.
Thesis Supervisor: Brian W. Anthony
Title: Research Scientist
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Acknowledgments
I would like to thank my research advisor, Dr. Brian Anthony, for giving me the
opportunity to work in such a rewarding research group and providing continuous
advice throughout the research process. I am very thankful for Dr. Anthony's support
and vision, which was critical to the success of this research.
I would also like to thank Matthew Gilbertson, whose incredible design and ma-
chining skills contributed to the experimental setup, and Shih-Yu Sun, whose brilliant
previous work on displacement and strain estimation is used throughout this thesis.
I would also like to thank Lauren Chai, Sisir Koppaka, John Lee, Dr. Victor Lempit-
sky, Javier Ramos, Dr. Kai Thomenius, and Dr. Bill Vannah for important support
in this work.
I would like to acknowledge Dr. Sheryl Gracewski, whose invaluable research
expertise and advising helped me start on an unbelievably rewarding path of research
and ultimately led me to where I am today.
Finally, I would like to thank my parents, Diane and Richard, and my sister,
Allyson, for their unwavering, loving support throughout my time at MIT and through-
out my entire life.
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Contents
1 Introduction 19
1.1 Breast Cancer 19
1.1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
1.1.2 Current Screening Methods . . . . . . . . . . . . . . . . . . . 20
1.2 Cardiovascular System Monitoring . . . . . . . . . . . . . . . . . . . . 21
1.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
1.2.2 Current Arterial Wall Stiffness Monitoring Methods . . . . . . 22
1.2.3 Current Blood Pressure Monitoring Methods . . . . . . . . . . 24
1.3 Introduction to Elastography . . . . . . . . . . . . . . . . . . . . . . 26
1.3.1 Quantitative Ultrasound Elastography . . . . . . . . . . . . . 27
1.3.2 Qualitative Ultrasound Elastography . . . . . . . . . . . . . . 27
1.3.3 Shear Wave Elastography . . . . . . . . . . . . . . . . . . . . 27
1.3.4 Intravascular Elastography . . . . . . . . . . . . . . . . . . . . 30
1.3.5 Vibro-Acoustography . . . . . . . . . . . . . . . . . . . . . . . 30
1.4 Importance of Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
1.4.1 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
1.4.2 Contribution . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
1.4.3 Application to Other Fields . . . . . . . . . . . . . . . . . . . 32
1.5 Outline of Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
1.6 Sum m ary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2 Theoretical Details 35
2.1 Inverse Problem and Details . . . . . . . . . . . . . . . . . . . . . . . 35
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2.1.1 Theoretical Workflow . . . . . . . . . . . . . . . . . . . . . 35
2.1.2 Forward Problem and B-Mode Generation . . . . . . . . . . . 38
2.1.3 Displacement Estimation Overview . . . . . . . . . . . . . . . 38
2.1.4 Optimization Techniques . . . . . . . . . . . . . . . . . . . . . 39
2.1.5 Multiscale Approach . . . . . . . . . . . . . . . . . . . . . . . 42
2.1.6 Sm oothing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
2.1.7 Starting and Ending Point . . . . . . . . . . . . . . . . . . . . 44
2.1.8 Error Calculation . . . . . . . . . . . . . . . . . . . . . . . . . 44
2.1.9 Arterial Stiffness and Pressure . . . . . . . . . . . . . . . . . . 44
2.2 Finite Element Implementation . . . . . . . . . . . . . . . . . . . . . 45
2.2.1 Boundary Conditions . . . . . . . . . . . . . . . . . . . . . . . 45
2.2.2 Modeling of Artery and Blood . . . . . . . . . . . . . . . . . . 46
2.2.3 Automatic Meshing . . . . . . . . . . . . . . . . . . . . . . . . 48
2.2.4 Integration with Abaqus . . . . . . . . . . . . . . . . . . . . . 53
2.2.5 Integration with an In-House Finite Element Code . . . . . . . 53
2.3 Reference Pressure Elimination . . . . . . . . . . . . . . . . . . . . . 54
2.3.1 Coordinate Optimization Theory . . . . . . . . . . . . . . . . 54
2.3.2 Initial Guess and Boundary Conditions . . . . . . . . . . . . . 59
2.4 Sum m ary . . . . . . . . . . . . . . . . . . . . 59
3 Experimental Details 61
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1
3.2 Experimental Setup . . . . . . . . . . . . . . . . . . . . . . . . . 6 1
3.3 Phantom Construction . . . . . . . . . . . . . . . . . . . . . . . 6 5
3.3.1 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5
3.3.2 Molds . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7
3.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2
4 Simulation Results and Discussion 73
4.1 Homogeneous Phantoms . . . . . 73
4.2 Heterogeneous Phantoms . . . . . 79
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4.3 Pressure Phantoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
4.4 Artery Phantoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
4.5 Elimination of the Reference Pressure . . . . . . . . . . . . . . . . . . 91
4.6 Sum m ary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
5 Experimental Results and Discussion 97
5.1 Homogeneous Phantoms . . . . . . . . . . . . . . . . . . . . . . . . . 97
5.2 Heterogeneous Phantoms. . . . . . . . . . . . . . . . . . . . . . . . . 99
5.3 Pressure Phantoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
5.4 Artery Phantoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
5.5 Sum m ary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
6 Conclusion 111
6.1 Sum m ary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
6.2 Future Work. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
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