1. TTK 4165 Signalbehandlingsteknikker i medisinsk bildediagnostikk
Signal Processing in Medical Imaging
Faglærer: Hans Torp
Institutt for sirkulasjon og bildediagnostikk
Story:
Myocard. Deseases important. Noninvasive methods desirable
(Viability, perfusion, mechanical stress/strain)
Ultrasound principles (one slide). Increasing aperture
Cardiac imaging from bathtube to realtime)
Stress echo
Poor image quality need for contrast
Perfusion imaging - second harmonic
Octave improves image quality
Doppler blood flow
important for valve and diastolic function
Color flow give detailed filling info, difficult to relate to regional function
Tissue Doppler more directly related to muscular movement
Integrated effect from apex
TVI simultaneous vel. Measurement over 2D plane
Displacement imaging
Strain rate and strain imaging
High frame-rate methods
Q-stress
Hans Torp
NTNU, Norway

2. Introduksjon Litt ultralydfysikk og historisk tilbakeblikk
Ultralyd avbildning
Ultralyd Doppler for måling/avbildning av hastighet
Oversikt over faget TTK4165
Story;
M-mode to real-time 2D
Next step 3D ??? No, No, ………
Stress echo
Poor image quality need for contrast
Perfusion imaging - second harmonic
Octave improves image quality
Hans Torp
NTNU, Norway

3. lecture overview Physical principles of ultrasound Ultrasound imaging
Ultrasound Doppler and flow imaging
Overview TTK4165
Story;
M-mode to real-time 2D
Next step 3D ??? No, No, ………
Stress echo
Poor image quality need for contrast
Perfusion imaging - second harmonic
Octave improves image quality
Hans Torp
NTNU, Norway

4. Sound field depends on source size and wavelength

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

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

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

8. 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

9. Ultrasound probe Focusing Steering and Focusing 50-200 elements
Strålefokusering kan også foregå elektronisk.
Ved å sende på de forskjellige elementene til litt forskjellig tid kan man få bidragene fra elementene til å følge en virtuell sirkelbue.
Send først på ytterste, så på innerste.
Man kan velge dybden på fokus ved å sette opp bestemte forsinkelser.
Elektronisk strålestyring som vist tidligere kankombineres med fokusering.
På mottaging kan man tilsvarende motta på alle elementer samtidig, men forsinkesignalet på de midterste elementene slik at man får en virtuell krumning også på mottaking.
Denne kan forandres under mottaking som vi skal se:
elements

10. Received Echoes from close objects2 1
Objects
probe
elements

11. Digital Beam Former Data per scanline: 2*10.000*128 = 2.5 Mb
A / D
134
#Channels:
128
# samples per channel:
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. 1996
System Five 128 channels
Elektronic scanning
Mekanisk scanning
2000
Vivid 7
128 kanaler
Elektronisk scanning
1986
CFM 700
5 channels
Mekanisk scanning

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

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

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

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

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

18. 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;

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

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

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

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

23. Real-time 3D imaging 2D matrix array
elements in a 1D array
32* *96 elements in a 2D array
elements
Cable
Electronics
Beamformer
50 x 1
elements
50 x 50
=2500
elements

24. Sanntid 3D
Azimuth
Elevation

25. 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

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

27. 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