UNIVERSITY OF HAWAII LIBRARY PHONOCARDIOGRAM SEGMENTATION A THESIS SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAI'I IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN ELECTRICAL ENGINEERING December 2005 By TangChuLin Thesis Committee: Todd Reed, Chairperson N.,Thomas Gaarder Anders Host-Madsen We certify that we have read this thesis and that, in our opinion, it is satisfactory in scope and quality as a thesis for the degree of Master of Science in Electrical Engmeering. 11 I Qlll I .H3 no. 4028 THESIS COMMITTEE Chairperson ii Acknowledgement I thank the committee members, Dr. Gaarder and Dr. Host-Madsen for all their support and guidance for the past two years. I am deeply indebted to my advisor Dr. Reed for his L. excellent technical mentoring and support in steering my career path. Much thanks to my Orincon friends for all their support and being so flexible with my schedule. I thank my professors at Loyola Marymount - Dr. Page and Dr. Marino - for believing in me and encouraging me to pursue a Graduate degree. Last be not least, I would like to thank my family - Mom, Dad (Shawn), Ryan, Bu - and Jon. They have been with me at every step, providing support, and encouragement. 111 Abstract Heart auscultation (the interpretation of heart sounds) is the primary tool used in screening patients for heart disease. While advanced techniques such as electrocardiograms exist, they are costly and not available in many developing countries. Heart auscultation is a subjective skill that can takes years of experience to master. Unfortunately, despite the number of patients and years of experience, it is documented that primary care physicians have poor auscultatory skills [10]. This work analyzes heart sound recordings known as phonocardiograms (PCG) uSing Wavelets and Principle Component Analysis (PCA). The primary goal is to segment key cardiac events in a heart sound signal. It is hoped that the results can be used in conjunction with other algorithms to provide a tool in heart auscultatory training and aid in automated heart diagnosis systems. IV Table of Contents ABSTRACT .............................................................................................................. IV LIST OF TABLES .................................................................................................. VIII LIST OF FIGURES ................................................................................................... IX 1 INTRODUCTION .................................................................................................1 2 CARDIAC ANATOMY .........................................................................................5 2.1 The Cardiac Cycle .................................................................................................................................. 5 2.2 The Primary Heart Sounds ................................................................................................................... 7 2.2.1 Heart Sound Frequency Spectrum ....................................................................................................... 9 2.2.2 Other Heart Sound Components ......................................................................................................... 9 3 THEORY ...........................................................................................................10 3.1 Fourier Transform ............................................................................................................................... 10 3.2 Short Time Fourier Transform ........................................................................................................... 12 3.3 Wavelet Analysis .................................................................................................................................. 16 3.3.1 Continuous Wavelet Transform ........................................................................................................ 16 3.3.2 Discrete Wavelet Transform ............................................................................................................. 18 3.3.3 Wavelet Synthesis ............................................................................................................................. 25 3.4 Principle Component Analysis ............................................................................................................ 28 3.4.1 Discussion and Properties of PC A .................................................................................................... 29 4 PHONOCARDIOGRAM SEGMENTATION ......................................................31 4.1 Segmentation Modules ......................................................................................................................... 33 4.1.1 Decimation ........................................................................................................................................ 33 v 4.1.2 Wavelet Decomposition .................................................................................................................... 48 4.1.2.1 The "Mother" Wavelet ............................................................................................................ 48 4.1.2.2 Heart Sound Wavelet Decomposition ...................................................................................... 50 4.1.2.3 Heart Sound Wavelet Synthesis ............................................................................................... 60 4.1.3 Finding Feature Signals ..................................................................................................................... 70 4.1.3.1 Finding the right PCs ............................................................................................................... 74 4.1.3.2 Summary of PCA Analyses ..................................................................................................... 77 4.1.4 Envelogram ....................................................................................................................................... 81 4.1.4.1 Primary Components ............................................................................................................... 81 4.1.4.2 "Other" Components ............................................................................................................... 87 5 RESULTS .........................................................................................................89 5.1 Performance Analysis: Sl and S2 Identification .............................................................................. 89 5.2 Performance Analysis: Component Boundaries .............................................................................. 90 5.2.1 Normal Heart Sound ......................................................................................................................... 90 5.2.2 Diastolic Atrial Gallop ...................................................................................................................... 91 5.2.3 Split S2 .............................................................................................................................................. 93 5.2.4 Early Aortic Stenosis ......................................................................................................................... 95 5.2.5 Ejection Click .................................................................................................................................... 97 5.2.6 Late Systolic ...................................................................................................................................... 99 5.2.7 Pan-Systolic .................................................................................................................................... 101 5.2.8 Systolic Mitral Prolapse .................................................................................................................. 103 5.3 Performance Analysis Summary ...................................................................................................... 106 6 CONCLUSION AND FUTURE WORK ............................................................ 112 7 APPENDiX ......................................................................................................113 7.1 Main Function ................................................................~ ................................................................... 113 7.2 Wavelet Decomposition, Reconstruction, PCA ............................................................................... 113 7.3 Primary Component Segmentation .................................................................................................. 115 7.4 "Other" Segmentation ....................................................................................................................... 118 vi 7.S Primary Component Labeling .......................................................................................................... 120 8 REFERENCES ................................................................................................ 126 vii List of Tables TABLE 1: DETAIL LEVEL FREQUENCY BAND 23 TABLE 2: WAVELET DECOMPOSITION INFORMATION TABLE 50 TABLE 3: SUMMARY OF WAVELET DECOMPOSITION ANALYSIS 59 TABLE 4: ENERGY CAPTURED BY PRINCIPLE COMPONENTS 72 TABLE 5: PRINCIPLE COMPONENT ENERGY DISTRIBUTION FOR EARLY AORTIC STENOSIS 74 TABLE 6: COMPONENT ENERGY DISTRIBUTION FOR PAN SYSTOLIC 75 TABLE