Ultrasound Imaging Using Coded Signals

228 Pages·2001·11.697 MB·English

by  Misaridis Th.

Ultrasound Imaging
Using Coded Signals
Thanassis Misaridis
CenterforFastUltrasoundImaging
TechnicalUniversityofDenmark
August 2001

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Contents
Contents i
Preface v
Abstract vii
Acknowledgements ix
Nomenclature xi
ListofFigures xiv
ListofTables xxv
0 Introduction 1
0.1 Potentialadvantagesofcodedexcitation . . . . . . . . . . . . . . . . . . . . . . . 1
0.2 LiteratureReview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
0.3 Thesisstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1 Modulatedsignals 5
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2 Signalbasics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3 Complexnotationofnarrowbandsignals . . . . . . . . . . . . . . . . . . . . . . 7
1.4 Correlationintegrals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.5 Waveformparametersandtheuncertaintyprinciple . . . . . . . . . . . . . . . . . 9
1.6 Thetime-bandwidthproduct(TB) . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2 Pulsecompressionandtheambiguityfunction 13
2.1 Filteringusingcomplexnotation . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2 Thematchedfilter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.3 Generalizedmatchedfilter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.4 Matchedfilterreceiverinultrasoundimaging . . . . . . . . . . . . . . . . . . . . 18
2.5 Theambiguityfunctionanditsproperties . . . . . . . . . . . . . . . . . . . . . . 20
i
2.6 Classificationofpulsecompressionwaveforms . . . . . . . . . . . . . . . . . . . 21
2.7 Resolutioninamatchedfilterreceiver . . . . . . . . . . . . . . . . . . . . . . . . 26
2.8 Mismatchedfiltering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.9 Optimalfilteringinspeckle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.10 Appropriatecompressionwaveformsandfiltersforultrasoundimaging . . . . . . 32
3 ThelinearFMsignalandotherFMwaveforms 35
3.1 ThelinearFMsignal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.2 SpectrumofthelinearFMsignal . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.3 Symmetrypropertiesandtheirimplications . . . . . . . . . . . . . . . . . . . . . 38
3.4 Thematchedfilterresponseandtheridgeambiguity . . . . . . . . . . . . . . . . 40
3.5 Mismatchedfiltering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.6 Gaininsignaltonoiseratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
3.7 Non-linearFMmodulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4 WeightingofFMsignalsandsidelobereductionforultrasoundimaging 47
4.1 Weightingintimeandfrequencydomain . . . . . . . . . . . . . . . . . . . . . . 47
4.2 Weightingfunctionsandtapering . . . . . . . . . . . . . . . . . . . . . . . . . . 48
4.3 Theeffectoftheultrasonictransduceronpulsecompression . . . . . . . . . . . . 50
4.4 Fresnelripplesandpaired-echoessidelobes . . . . . . . . . . . . . . . . . . . . . 51
4.5 Amplitudeandphasepredistortion . . . . . . . . . . . . . . . . . . . . . . . . . . 53
4.6 Proposedexcitation/compressionscheme . . . . . . . . . . . . . . . . . . . . . . 54
5 Phase-modulatedsignals 61
5.1 Phasemodulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
5.2 Binarysequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
5.3 Polyphasecodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
5.4 Hadamardmatrices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
5.5 Sidelobereductionforphase-encodedsequences . . . . . . . . . . . . . . . . . . 69
5.6 Disadvantagesofphase-codingforultrasoundimaging . . . . . . . . . . . . . . . 70
6 Ultrasoundimagingwithcodedexcitation-Simulationresults 71
6.1 Intensityconsiderations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
6.2 Expectedsignal-to-noiseratioimprovement . . . . . . . . . . . . . . . . . . . . . 73
6.3 ImagingwithlinearFMsignals-SimulationresultsusingFieldII . . . . . . . . . 80
6.4 Imagingwithnon-linearFMsignals . . . . . . . . . . . . . . . . . . . . . . . . . 84
6.5 Imagingwithcomplementarycodes . . . . . . . . . . . . . . . . . . . . . . . . . 85
6.6 Evaluationofresolutionandcompression . . . . . . . . . . . . . . . . . . . . . . 85
6.7 Pulsecompressionandarrayimaging . . . . . . . . . . . . . . . . . . . . . . . . 88
7 Clinicalevaluationofcodedimaging 91
7.1 Experimentalsetup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
7.2 Phantomimageswithcodedexcitation . . . . . . . . . . . . . . . . . . . . . . . 96
7.3 Clinicalimageswithcodedexcitation . . . . . . . . . . . . . . . . . . . . . . . . 100
8 Waveformdiversityforfastultrasoundimaging 105
ii