Non-linear acoustics in Ultrasound Imaging Hans Torp Department of Physiology and Biomedical Engineering NTNU NTNUNorway Hans Torp NTNU, Norway

Non-linear acoustics in Ultrasound Imaging Body wall object Nonlinear propagation Transducer nonlinear scattering Hans Torp NTNU, Norway

Nonlinear propagation Transmitted pulsePulse after 6cm propagation frequency fo 2fo 3fo frequency fo 2fo 3fo

Received signal is filtered by 1. transducer 2. Frequency dependent attenuation Hans Torp NTNU, Norway

Measured RF- spectrum Frequency range 1- 4 MHz Signal from ventricular septum Noise from LV cavity Hans Torp NTNU, Norway

Fundamental and second harmonic signal separated by filter 450 Fundamental2. harmonicSignal from septum Noise from LV cavity Hans Torp NTNU, Norway

Water tank experiment Full band 2nd Harmonic Hans Torp NTNU, Norway

Second harmonic imaging Reverberation noise is suppressed Conventional Bmode imaging ftx=3.4 MHz, frx=3.4 MHz 2.harmonic Bmode imaging ftx=1.7 MHz, frx=3.4 MHz x Frequency Signal Noise Hans Torp NTNU, Norway

Cardiac examples 3.5 MHz probe FundamentalOctave Hans Torp NTNU, Norway

Cardiac examples 5 MHz probe Fundamental Octave Hans Torp NTNU, Norway

Cardiac examples 5 MHz probe FundamentalOctave Hans Torp NTNU, Norway

Brain - neonatal 5 MHz probe FundamentalOctave Hans Torp NTNU, Norway

Brain - 18 week fetus 5 MHz probe FundamentalOctave Hans Torp NTNU, Norway

Brain - 18 week fetus 5 MHz probe Fundamental Octave Hans Torp NTNU, Norway

Summary 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