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Hans Torp NTNU, Norway. Artefakter I ultralydbilder. Hans Torp Department of Physiology and Biomedical Engineering NTNU Norway. Artefakter I ultralydbilder. Anisotropi og speckle Hindringer for ultralydbølgene Nær probe - -> redusert lateral oppløsning

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## Artefakter I ultralydbilder

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**Hans Torp**NTNU, Norway Artefakter I ultralydbilder Hans Torp Department of Physiology and Biomedical Engineering NTNU Norway**Artefakter I ultralydbilder**• Anisotropi og speckle • Hindringer for ultralydbølgene • Nær probe - -> redusert lateral oppløsning • Avstand fra probe -> Skygge • Reverberasjoner • Aberasjoner**Hindring i avstand fra transducergir skygge i**ultralydbildet • videoklipp**Hindring nær transducergir redusert effektiv aperture**• videoklipp**Probe-diameter**D F: Fokaldybde L Oppløsning (skarphet) D Blenderåpning F-tall f# = F/D Bølgelengde: L Lateral oppløsning: f# L F: Fokaldybde Eksempel Foto: L = 0.9 e-3 mm f# = 5.6 Oppløsning: 0.005 mm ~ 50000 dpi Eksempel Ultralyd: L = 0.5 mm (3 MHz) f# = 8cm/2cm= 4 Oppløsning: 2 mm ~ 125 dpi Større probe -> Bedre oppløsning Høyere frekvens -> Bedre oppløsning**Gitterlober**Gitterlobe Kraftig ekko**Acoustical noise due to**- reverberations - aberrations Cardiac ultrasound imaging**Pulse after 6cm propagation**Hans Torp NTNU, Norway Pulse at transducer surface Non-linear acoustics in Ultrasound Imaging Transducer Nonlinear propagation Body wall**2. harmonic**Hans Torp NTNU, Norway Fundamental and second harmonic signal separated by filter 50 100 150 200 250 300 350 400 450 20 40 60 80 100 Fundamental Signal from septum Noise from LV cavity**Hans Torp**NTNU, Norway Second harmonic imagingReverberation noise is suppressed 80 60 40 20 0 -20 0 1 2 3 4 5 6 x 10 Frequency 2.harmonic Bmode imaging ftx=1.7 MHz, frx=3.4 MHz Conventional Bmode imaging ftx=3.4 MHz, frx=3.4 MHz Signal Noise**Hans Torp**NTNU, Norway Cardiac examples 5 MHz probe Octave Fundamental**Hans Torp**NTNU, Norway Cardiac examples 5 MHz probe Fundamental Octave**Hans Torp**NTNU, Norway Brain - neonatal 5 MHz probe Fundamental Octave**Hans Torp**NTNU, Norway Brain - 18 week fetus 5 MHz probe Fundamental Octave**Hans Torp**NTNU, Norway Brain - 18 week fetus 5 MHz probe Fundamental Octave

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