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

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Presentation on theme: "TTK 4165 Signalbehandlingsteknikker i medisinsk bildediagnostikk Signal Processing in Medical Imaging Faglærer: Hans Torp Institutt for sirkulasjon og."— Presentation transcript:

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

2 Introduksjon Litt ultralydfysikk og historisk tilbakeblikkLitt ultralydfysikk og historisk tilbakeblikk Ultralyd avbildningUltralyd avbildning Ultralyd Doppler for måling/avbildning av hastighetUltralyd Doppler for måling/avbildning av hastighet Oversikt over faget TTK4165Oversikt over faget TTK4165 Hans Torp NTNU, Norway

3 lecture overview Physical principles of ultrasoundPhysical principles of ultrasound Ultrasound imagingUltrasound imaging Ultrasound Doppler and flow imagingUltrasound Doppler and flow imaging Overview TTK4165Overview TTK4165 Hans Torp NTNU, Norway

4 Sound field depends on source size and wavelength

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

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

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

8 Fourier transform - measure bloodflowFourier transform - measure bloodflow Gaussian Random process - ultrasound signalGaussian Random process - ultrasound signal Analog computer diff. equation solver - model of the cardiovascular systemAnalog computer diff. equation solver - model of the cardiovascular system Bernouli equation - from blood velocity to pressureBernouli equation - from blood velocity to pressure

9 Ultrasound probe Focusing Steering and Focusing 50-200 elements

10 Received Echoes from close objects probe elements Objects 1 2

11 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

12 1986 CFM 700 5 channels Mekanisk scanning 1996 System Five 128 channels Elektronic scanning Mekanisk scanning 2000 Vivid 7 128 kanaler Elektronisk scanning

13 Real-time 2D B-mode Wall motion assessment ))) Hans Torp NTNU, Norway

14 Ultrasound Probes 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

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

16 Image resolution D aperture F: Focal depth F-number f# = F/D Wavelength: L ”Dot-size”: f#  L 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 Probe-diameter D F: Focal depth L

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

18 3D Transvaginal ultrasound 3D Transvaginal ultrasound The Lancet: In-vivo three-dimensional ultrasound reconstructions in the embryonic and early fetal period Harm-Gerd Blaas 1, Sturla H. Eik-Nes 1, Sevald Berg 2, Hans Torp 2 ; In-vivo three-dimensional ultrasound reconstructions in the embryonic and early fetal period

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

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

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

22 Strain rate L v1v1 v2v2 Tissue velocityStrain rate SR Adapted from J-U. Voigt and A. Heimdal Shortening No change Elongation Wall motion quantification Systole Early relax. Atrial systole Curved M-mode

23 Real-time 3D imaging 2D matrix array 32-192 elements in a 1D array32-192 elements in a 1D array 32*32... 96*96 elements in a 2D array32*32... 96*96 elements in a 2D array 1000 - 10000 elements1000 - 10000 elements CableCable ElectronicsElectronics BeamformerBeamformer 50 x 1 elements 50 x 50 =2500 elements

24 Sanntid 3D Azimuth Elevation

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

26 4D Color Imaging (ECG Gated) Gated from 7 heart beatsGated from 7 heart beats High frame rates (17-35 frames / second)High frame rates (17-35 frames / second) High Color sensitivityHigh Color sensitivity High Color resolutionHigh Color resolution

27 TTK4165 Overview Pulse Echo principlePulse Echo principle Ultrasound beamformingUltrasound beamforming General imaging systemGeneral imaging system Ultrasound imaging systemUltrasound imaging system Doppler – blood velocity measurement and imagingDoppler – blood velocity measurement and imaging Patient safety issuesPatient safety issues Ultrasound contrast imagingUltrasound contrast imaging 3D imaging3D imaging


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