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TTK 4165

Hans Torp NTNU, Norway. TTK 4165. Signalbehandlingsteknikker i medisinsk bildediagnostikk Signal Processing in Medical Imaging Faglærer: Hans Torp Institutt for sirkulasjon og bildediagnostikk. Hans Torp NTNU, Norway. lecture overview. Physical principles of ultrasound

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TTK 4165

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  1. Hans Torp NTNU, Norway TTK 4165 Signalbehandlingsteknikker i medisinsk bildediagnostikk Signal Processing in Medical Imaging Faglærer: Hans Torp Institutt for sirkulasjon og bildediagnostikk

  2. Hans Torp NTNU, Norway lecture overview • Physical principles of ultrasound • Ultrasound imaging • Ultrasound Doppler and flow imaging • Overview TTK4165

  3. Sound field depends on source size and wavelength

  4. Echoes from tissue structures are received and displayed First Cardiac trials by Edler and Hertz in 1953 Hans Torp NTNU, Norway Ultrasonic M-Mode (Motion Mode)

  5. Hans Torp NTNU, Norway Real-time Ultrasound B-mode 1974 Vis film N. Bom & al. “Multiscan EchoCardiograph” Ultrasound in Medicine aug. 74

  6. Blood velocity Mitral inflow Normal relaxation Delayed relaxation Doppler blood flow meter Pedof 1976

  7. Fourier transform - measure bloodflow • Gaussian Random process - ultrasound signal • Analog computer diff. equation solver- model of the cardiovascular system • Bernouli equation- from blood velocity to pressure

  8. Ultrasound probe Focusing Steering and Focusing 50-200 elements

  9. 2 Received Echoes from close objects 1 Objects probe elements

  10. A / D 134 134 134 134 134 134 134 134 134 134 134 134 134 134 134 A / D 134 134 134 134 134 134 134 134 134 134 134 134 134 134 134 A / D 134 134 134 134 134 134 134 134 134 134 134 134 134 134 134 A / D 134 134 134 134 134 134 134 134 134 134 134 134 134 134 134 A / D 134 134 134 134 134 134 134 134 134 134 134 134 134 134 134 A / D 134 134 134 134 134 134 134 134 134 134 134 134 134 134 134 A / D 134 134 134 134 134 134 134 134 134 134 134 134 134 134 134 Digital Beam Former #Channels: 128 # samples per channel: 10.000 • Data per scanline: 2*10.000*128 = 2.5 Mb • Data per image: 2.5*100 = 250 Mb • Data per second: 40* 250 Mb = 10 Gb

  11. 1996 System Five 128 channels Elektronic scanning Mekanisk scanning 2000 Vivid 7 128 kanaler Elektronisk scanning 1986 CFM 700 5 channels Mekanisk scanning

  12. Hans Torp NTNU, Norway Real-time 2D B-modeWall motion assessment ))) )))

  13. Linear array High resolution Limited width Curve-linear array Large image width Large near field Phased array Small footprint 90 deg. sector format Hans Torp NTNU, Norway Ultrasound Probes

  14. Heart, 4 chamber view Kidney Fetus 3 ½ mnd Liver Twin fetus Ultrasound imaging can be applied to almost all human organs Ultrasound imaging: Measure dimensions, areas, volumes Study anatomical details Assessment of muscle contraction Heart-valve function

  15. Probe-diameter D F: Focal depth L Image resolution D aperture F-number f# = F/D Wavelength: L ”Dot-size”: f#  L F: Focal depth Camera example L = 0.9 e-3 mm f# = 5.6 Resolution: 0.005 mm ~ 50000 dpi Infrared camera gives lower resolution Ultrasound example L = 0.5 mm (3 MHz) f# = 8cm/2cm= 4 Resolution: 2 mm ~ 125 dpi Larger probe -> improved resolution Higher frequency -> improved resolution

  16. Embryo 7 weeks. Ca 13 mm length • Computer-simulated ultrasound image • Higher frequency -> better resolution

  17. 3D Transvaginal ultrasoundThe Lancet:In-vivo three-dimensional ultrasound reconstructions in the embryonic and early fetal periodHarm-Gerd Blaas 1, Sturla H. Eik-Nes 1, Sevald Berg 2, Hans Torp 2;

  18. 18 weeks Limb development in Norway 20th century 12 weeks

  19. PW Doppler: Velocity from one point Color flow imaging: Velocities in the whole image Color M-mode: Velocities along a line Color Doppler velocity imaging

  20. Curved M-mode Systole Atrial systole Early relax. Hans Torp NTNU, Norway Tissue Velocity Imaging Moving upward Moving downward

  21. Wall motion quantification Curved M-mode Systole Atrial systole Early relax. Strain rate Tissue velocity Strain rate v1 SR L v2 Shortening No change Elongation Adapted from J-U. Voigt and A. Heimdal

  22. Real-time 3D imaging2D matrix array 50 x 1 elements • 32-192 elements in a 1D array • 32*32 ... 96*96 elements in a 2D array • 1000 - 10000 elements • Cable • Electronics • Beamformer 50 x 50 =2500 elements

  23. Azimuth Elevation Sanntid 3D

  24. 4D Volume Imaging Increased elevation width Standard setup • No ECG gating • Volume rendering / orthogonal slicing • Volume size: ~20 x 80º / ~35 x 45º • Volume rate: 17-25

  25. 4D Color Imaging (ECG Gated) • Gated from 7 heart beats • High frame rates (17-35 frames / second) • High Color sensitivity • High Color resolution

  26. TTK4165 Overview • Pulse Echo principle • Ultrasound beamforming • General imaging system • Ultrasound imaging system • Doppler – blood velocity measurement and imaging • Patient safety issues • Ultrasound contrast imaging • 3D imaging

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