non-linear acoustics in ultrasound imaging hans torp department of physiology and biomedical...
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Non-linear acoustics in Ultrasound ImagingNon-linear acoustics in Ultrasound Imaging
Hans TorpHans Torp
Department of Physiology and Biomedical EngineeringDepartment of Physiology and Biomedical Engineering
NTNUNTNU
NorwayNorway
Hans TorpNTNU, Norway
Non-linear acoustics in Non-linear acoustics in Ultrasound ImagingUltrasound Imaging
Body wall
object
Nonlinear propagation
Transducer
nonlinear scattering
Hans TorpNTNU, Norway
Nonlinear propagationNonlinear propagation
0.5 1 1.5 2 2.5 3 3.5
x 10-6
-0.015
-0.01
-0.005
0
0.005
0.01
0.015
0.02
Transmitted pulse
0.5 1 1.5 2 2.5 3 3.5
x 10-6
-0.04
-0.02
0
0.02
0.04
0.06
0.08
0.1
0.12
Pulse after 6cm propagation
0 1 2 3 4 5 6 7 8 9 10
x 106
-40
-30
-20
-10
0
10
20
0 1 2 3 4 5 6 7 8 9 10
x 106
-40
-30
-20
-10
0
10
20
frequencyfo 2fo 3fo frequencyfo 2fo 3fo
Received signal is filtered byReceived signal is filtered by1. transducer1. transducer2. Frequency dependent attenuation2. Frequency dependent attenuation
0 2 4 6 8 10x 106
-70
-60
-50
-40
-30
-20
-10
0
Hans TorpNTNU, Norway
Measured RF- spectrumMeasured RF- spectrumFrequency range 1- 4 MHzFrequency range 1- 4 MHz
0 1 2 3 4 5x 106
-20
0
20
40
60
80
Signal from ventricular septumNoise from LV cavity
Hans TorpNTNU, Norway
Fundamental and second harmonic Fundamental and second harmonic signal separated by filtersignal separated by filter
0 1 2 3 4 5x 106
-20
0
20
40
60
80
450
Fundamental 2. harmonicSignal from septumNoise from LV cavity
-500 0 5000
50
100
150
200
250
-10 0 100
50
100
150
200
250
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Water tank experimentWater tank experiment
0 2 4 6x 106
-20
0
20
40
60
80
100
Full band 2nd Harmonic
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Second harmonic imagingSecond harmonic imagingReverberation noise is suppressedReverberation noise is suppressed
Conventional Bmode imagingftx=3.4 MHz, frx=3.4 MHz
2.harmonic Bmode imagingftx=1.7 MHz, frx=3.4 MHz
0 1 2 3 4 5x 106
-20
0
20
40
60
80
FrequencySignal
Noise
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Cardiac examples 3.5 MHz probeCardiac examples 3.5 MHz probe
Fundamental Octave
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Cardiac examples 5 MHz probeCardiac examples 5 MHz probe
Fundamental OctaveHans TorpNTNU, Norway
Cardiac examples 5 MHz probeCardiac examples 5 MHz probe
Fundamental OctaveHans TorpNTNU, Norway
Brain - neonatal 5 MHz probeBrain - neonatal 5 MHz probe
Fundamental OctaveHans TorpNTNU, Norway
Brain - 18 week fetus 5 MHz probeBrain - 18 week fetus 5 MHz probe
Fundamental OctaveHans TorpNTNU, Norway
Brain - 18 week fetus 5 MHz probeBrain - 18 week fetus 5 MHz probe
Fundamental Octave
Hans TorpNTNU, Norway
SummarySummary
•Harmonic distortion by wavepropagation is significant in medical ultrasound
•Acoustical noise is suppressed by filtering out the 2. Harm. Component
•Carefull pulse design to obtain short pulse with low 2. Harm. Content
•Improved elevation focusing is observed