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TTK 4165
Signalbehandlingsteknikker i
medisinsk bildediagnostikk
Signal Processing in Medical Imaging
Faglærer: Hans TorpInstitutt for sirkulasjon og bildediagnostikk
Hans TorpNTNU, Norway
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Introduksjon 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 TorpNTNU, Norway
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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 TorpNTNU, Norway
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Sound field depends on source size and Sound field depends on source size and wavelengthwavelength
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Ultrasonic M-Mode (Motion Mode)Ultrasonic M-Mode (Motion Mode)
Hans TorpNTNU, Norway
Echoes from tissue structures are received and displayed
First Cardiac trials by Edler and Hertz in 1953
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Real-time Ultrasound B-mode Real-time Ultrasound B-mode 19741974
N. Bom & al. “Multiscan EchoCardiograph” Ultrasound in Medicine aug. 74
Hans TorpNTNU, Norway
Vis film
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Doppler blood flow meter Pedof 1976Doppler blood flow meter Pedof 1976Blood velocity Mitral inflow
Normal relaxation
Delayed relaxation
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• Fourier transform - measure bloodflowFourier transform - measure bloodflow
• Gaussian Random process Gaussian Random process - ultrasound signal- ultrasound signal
• Analog computer diff. equation solverAnalog computer diff. equation solver- model of the cardiovascular system - model of the cardiovascular system
• Bernouli equationBernouli equation- from blood velocity to pressure- from blood velocity to pressure
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Ultrasound probeUltrasound probe
Fokus
Focusing Steering and Focusing
50-200 elements 50-200 elements
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Received Echoes Received Echoes from close objectsfrom close objects
probeelements
Objects
1
2
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Digital Beam FormerDigital Beam Former
A / D134134134134134134134134134134134134134134134
A / D134134134134134134134134134134134134134134134
A / D134134134134134134134134134134134134134134134
A / D134134134134134134134134134134134134134134134
A / D134134134134134134134134134134134134134134134
A / D134134134134134134134134134134134134134134134
A / D134134134134134134134134134134134134134134134
#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
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1986CFM 700 5 channelsMekanisk scanning
1996System Five 128 channelsElektronic scanningMekanisk scanning
2000Vivid 7 128 kanalerElektronisk scanning
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Real-time 2D B-modeReal-time 2D B-modeWall motion assessmentWall motion assessment
))) )))
Hans TorpNTNU, Norway
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Ultrasound ProbesUltrasound Probes
Linear arrayHigh resolutionLimited width
Curve-linear arrayLarge image widthLarge near field
Phased arraySmall footprint90 deg. sector format
Hans TorpNTNU, Norway
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Ultrasound imaging can be applied Ultrasound imaging can be applied to almost all human organsto almost all human organs
Liver Fetus 3 ½ mnd
Kidney
Twin fetus
Ultrasound imaging:Measure dimensions, areas, volumesStudy anatomical detailsAssessment of muscle contractionHeart-valve function
Heart, 4 chamber view
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Image resolutionImage resolution
Daperture
F:
Foc
al d
epth
F-number f# = F/D
Wavelength: L
”Dot-size”: f# L
Camera exampleL = 0.9 e-3 mmf# = 5.6Resolution: 0.005 mm ~ 50000 dpiInfrared camera gives lower resolution
Ultrasound exampleL = 0.5 mm (3 MHz)f# = 8cm/2cm= 4 Resolution: 2 mm ~ 125 dpi
Larger probe -> improved resolutionHigher frequency -> improved resolution
Probe-diameterD
F:
Foc
al d
epth
L
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•Computer-simulated ultrasound image•Higher frequency -> better resolution
Embryo 7 weeks. Ca 13 mm length
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3D Transvaginal ultrasound3D Transvaginal ultrasoundThe 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;
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Limb development in Norway 20Limb development in Norway 20thth century century
12 weeks 18 weeks
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Color Doppler velocity imagingColor Doppler velocity imaging
PW Doppler: Velocity from one point
Color flow imaging:Velocities in the whole image
Color M-mode: Velocities along a line
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Tissue Velocity ImagingTissue Velocity Imaging
Moving upwardMoving downward
SystoleEarlyrelax.
Atrialsystole
Curved M-mode
Hans TorpNTNU, Norway
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Strain rateStrain rate
Lvv
SR 12
Lv1v2
Tissue velocity Strain rate
SR
Adapted from J-U. Voigt and A. Heimdal
ShorteningNo changeElongation
Wall motion quantification
SystoleEarlyrelax.
Atrialsystole
Curved M-mode
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Real-time 3D imagingReal-time 3D imaging2D matrix array2D matrix array
• 32-192 elements in a 1D 32-192 elements in a 1D arrayarray
• 32*32 ... 96*96 elements 32*32 ... 96*96 elements in a 2D arrayin a 2D array
• 1000 - 10000 elements1000 - 10000 elements
• CableCable
• ElectronicsElectronics
• BeamformerBeamformer
50 x 1elements
50 x 50=2500elements
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Sanntid 3DSanntid 3D
Azimuth
Elevation
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4D Volume Imaging4D Volume Imaging
• No ECG gatingNo ECG gating
• Volume rendering / orthogonal Volume rendering / orthogonal slicingslicing
• Volume size: Volume size: ~20 x 80º / ~35 x 45º~20 x 80º / ~35 x 45º
• Volume rate: 17-25Volume rate: 17-25
Standard setup Increased elevation width
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4D Color Imaging (ECG Gated)4D Color Imaging (ECG Gated)
• Gated from 7 heart Gated from 7 heart beatsbeats
• High frame rates High frame rates (17-35 frames / (17-35 frames / second)second)
• High Color sensitivityHigh Color sensitivity
• High Color resolutionHigh Color resolution
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TTK4165 OverviewTTK4165 Overview
• Pulse Echo principlePulse Echo principle
• Ultrasound beamformingUltrasound beamforming
• General imaging system General imaging system
• Ultrasound imaging system Ultrasound 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