MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp
description
Transcript of MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp
![Page 1: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/1.jpg)
MEDT8002 Ultralyd bildediagnostikk
Faglærer: Hans Torp
Institutt for sirkulasjon og bildediagnostikk
Hans TorpNTNU, Norway
![Page 2: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/2.jpg)
New development in color New development in color DopplerDoppler
“Blood motion imaging” “Blood motion imaging”
Arteria bracialisConventionalColor Doppler
Arteria bracialisBlood motion imaging
Carotis communisBlood motion imaging
Hans TorpNTNU, Norway
![Page 3: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/3.jpg)
University(NTNU) - Industry(Vingmed)University(NTNU) - Industry(Vingmed)
1986 CFM 700 First color Dopplerwith mechanical scanning
Beam-adder
442
BFx
1995 System Five Digital beam former>Higher framerate>RF-data for research>Tissue Doppler
2000 Vivid 7 Real-time processingwith PC technology
![Page 4: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/4.jpg)
Data acquistion in Data acquistion in color flow imagingcolor flow imaging
Beam k-1 Beam k Beam k+1
Number of pulses in each direction
3 – 15
Frame rate reduction compared to B-mode
![Page 5: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/5.jpg)
2D Color flow imaging2D Color flow imaging
1. Limited information content in the signal, i.e. short observation time, low signal-to-noise ratio, and low Nyquist velocity limit.
2. Insufficient signal processing/display.
Full spectrum analysis in each point of the sector is difficult to visualize.
![Page 6: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/6.jpg)
Color mapping typesColor mapping types
Hans TorpNTNU, Norway
Power Doppler (Angio)
Brightnes ~ signal power
Color flow
Brightnes ~ signal powerHue ~ Velocity
Color flow ”Variance map”
Hue & Brightnes ~ VelocityGreen ~ signal bandwidth
![Page 7: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/7.jpg)
Color scale for velocity and - spreadColor scale for velocity and - spread
•• •
•••
••
•
•• •• • •
••••
•••
••••
•
••
•••
•
•
•
• • ••
•
•
•
•
•••
••••
••
•••• •
••
••••
••
•••
•••
•
• H¹H¤H‚
•
•
•
y
x
Ao
LV
LA
Power
Bandwidth
Aortic insufficiency
Hans TorpNTNU, Norway
![Page 8: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/8.jpg)
Color flow imaging Color flow imaging Mitral valve blood flowMitral valve blood flow
Normal mitral valve Stenotic mitral valve
Hans TorpNTNU, Norway
![Page 9: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/9.jpg)
Autocorrelation methodAutocorrelation methodSensitive to clutter noiseSensitive to clutter noise
)exp(i )G(
)exp(i )G( d i m { R ( 1 ) }
r e { R ( 1 ) }π
- πG (ω )
πω- π
Phase angle of R(1) substantially reduced due to low frequency clutter signalClutter filter stopband much more critical than for spectral Doppler
![Page 10: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/10.jpg)
How to perform clutter filter in How to perform clutter filter in color flow imaging?color flow imaging?
Beam k-1 Beam k Beam k+1
Signal discontinuity causes ringing in high-pass filters
Raw signal from beam k
Signal after high-pass filter
Lost settling time
![Page 11: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/11.jpg)
How to perform clutter filter in How to perform clutter filter in color flow imaging?color flow imaging?
Beam k-1 Beam k Beam k+1
Signal discontinuity causes ringing in high-pass filters
Raw signal from beam k
Signal after high-pass filter
Lost settling time
![Page 12: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/12.jpg)
Color flow scanning strategiesColor flow scanning strategies
B-mode scanning
Mechanical scanning
+ No settling time clutter filter- low frame rate
Electronic scanning Packet acquisition- Settling time clutter filter+flexible PRF without loss in frame rate
Electronic scanning continuous acquisition+ no settling time clutter filter+ High frame rate- low PRF (=frame rate)
scanning directiontim
e
![Page 13: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/13.jpg)
Color flow imaging with a Color flow imaging with a mechanical probemechanical probe
v = W*FR
Image width WFrame rate FRSweep velocity v= W*FR
Virtual axial velocity: vr= v*cotan()
vr
v
Example:Image width W = 5 cmFrame rate FR =20 fr/secAngle with beam = 45 deg.Sweep velocity v= 1 m/s
Virtual axial velocity: vr= 1 m/s
vr > max normal blood flow velocities!
![Page 14: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/14.jpg)
Color flow imaging with a Color flow imaging with a mechanical probemechanical probe
W= N*b
v = W*FR
Beamwidth (Rayleigh criterion): bEffective number of beams: N =W/bFrame Rate: FR
Signal from stationary scatterer
N*Fr*t
Clutter signal bandwidth: 2*N*FR
Power spectrum
Clutter filter cutoff frequency: fc > N*FR Frequency components < fc removed
![Page 15: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/15.jpg)
Minimum detectable Doppler shiftMinimum detectable Doppler shift
Frame rate Frame rate FR =1 Hz FR =1 Hz FR = 10 Hz FR=20 Hz FR = 10 Hz FR=20 HzWidth (# beams)Width (# beams)N=30N=30 30 Hz30 Hz 300 Hz300 Hz 600 Hz 600 HzN=70N=70 70 Hz70 Hz 700 Hz700 Hz1400 Hz1400 Hz
Clutter filter cutoff frequency: fc > N*FR(transit time effect mechanical scan)
Cardiac flow imaging: fo= 2 MHz, 15 mm aperture, beamwidth 3 mm30 beams covers the left ventriclefc = 600 Hz ~ 0.21 m/sec. lower velocity limit
![Page 16: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/16.jpg)
Color flow imaging with a Color flow imaging with a mechanical probemechanical probe
v = W*FR
Reflected wavedoes not hit the transducer
Max Dopplershift 600 Hz~ 0.21 m/sec
![Page 17: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/17.jpg)
Atlanta, GA april 1986Atlanta, GA april 1986
Vingmed, introduced Vingmed, introduced CFMCFM The first commercial The first commercial
colorflow imaging scanner colorflow imaging scanner with mechanical probewith mechanical probe
Horten, Norway Horten, Norway september 2001september 2001
GE-Vingmed closed down GE-Vingmed closed down production line for production line for CFMCFM
after 15 years of continuous after 15 years of continuous productionproduction
![Page 18: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/18.jpg)
Minimum detectable Doppler shiftMinimum detectable Doppler shiftClutter filter cutoff frequency: fc > N*FR
Frame rate Frame rate FR =1 Hz FR =1 Hz FR = 10 Hz FR = 10 Hz FR=20 Hz FR=20 HzWidth (# beams)Width (# beams)N=30N=30 30 Hz30 Hz 300 Hz300 Hz 600 Hz 600 HzN=70N=70 70 Hz70 Hz 700 Hz700 Hz1400 Hz1400 Hz
Periferal vessel imaging with fo= 10 MHzMechanical scanning: fc = 1400 Hz ~ 108 mm/sec. Electronic scanning: fc = 30 Hz ~ 2.3 mm/sec.
Packet acquisition (P=10): Frame rate = 35 frames/secContinuous acquisition: Frame rate = 350 frames/sec
![Page 19: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/19.jpg)
Combining tissue and flowCombining tissue and flowContinuous sweep acquisitionContinuous sweep acquisition
+
Brachial artery
![Page 20: MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp](https://reader033.fdocuments.in/reader033/viewer/2022061615/568162ca550346895dd355b7/html5/thumbnails/20.jpg)
Temporal averaging for mean Temporal averaging for mean frequency estimatorfrequency estimator
Example:
Effect of averaging R1 :
Variance of angle(R1)reduced by factor 24!
Effect of averaging angle(R1):
Variance reduction factor=4
)1(*)()1(ˆ1
nxnxR kk
N
nk k=1 : 4, uncorrelated signal packets