1 / 20

MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp

Hans Torp NTNU, Norway. MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp Institutt for sirkulasjon og bildediagnostikk. Hans Torp NTNU, Norway. New development in color Doppler “Blood motion imaging” . Arteria bracialis Conventional Color Doppler. Arteria bracialis

toya
Download Presentation

MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Hans Torp NTNU, Norway MEDT8002 Ultralyd bildediagnostikk Faglærer: Hans Torp Institutt for sirkulasjon og bildediagnostikk

  2. Hans Torp NTNU, Norway New development in color Doppler“Blood motion imaging” Arteria bracialis ConventionalColor Doppler Arteria bracialis Blood motion imaging Carotis communis Blood motion imaging

  3. Beam- adder  2  4 4 BFx • System Five • Digital beam former • >Higher framerate • >RF-data for research • >Tissue Doppler 2000 Vivid 7 Real-time processing with PC technology 1986 CFM 700 First color Doppler with mechanical scanning University(NTNU) - Industry(Vingmed)

  4. Beam k-1 Beam k Beam k+1 Data acquistion in color flow imaging Number of pulses in each direction 3 – 15 Frame rate reduction compared to B-mode

  5. 2D 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.

  6. Hans Torp NTNU, Norway Color mapping types Power Doppler (Angio) Brightnes ~ signal power Color flow Brightnes ~ signal power Hue ~ Velocity Color flow ”Variance map” Hue & Brightnes ~ Velocity Green ~ signal bandwidth

  7. Hans Torp NTNU, Norway Color scale for velocity and - spread Power Band width Aortic insufficiency

  8. Hans Torp NTNU, Norway Color flow imaging Mitral valve blood flow Normal mitral valve Stenotic mitral valve

  9. Autocorrelation methodSensitive to clutter noise Phase angle of R(1) substantially reduced due to low frequency clutter signal Clutter filter stopband much more critical than for spectral Doppler

  10. Beam k-1 Beam k Beam k+1 How to perform clutter filter in color flow imaging?

  11. Beam k-1 Beam k Beam k+1 How to perform clutter filter in color flow imaging?

  12. scanning direction Color flow scanning strategies time B-mode scanning Electronic scanning continuous acquisition + no settling time clutter filter + High frame rate - low PRF (=frame rate) 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

  13. Color flow imaging with a mechanical probe v = W*FR v vr  Example: Image width W = 5 cm Frame rate FR =20 fr/sec Angle with beam  = 45 deg. Sweep velocity v= 1 m/s Virtual axial velocity: vr= 1 m/s vr > max normal blood flow velocities! Image width W Frame rate FR Sweep velocity v= W*FR Virtual axial velocity: vr= v*cotan()

  14. Signal from stationary scatterer N*Fr*t Power spectrum Clutter signal bandwidth: 2*N*FR Clutter filter cutoff frequency: fc > N*FR Frequency components < fc removed Color flow imaging with a mechanical probe v = W*FR W= N*b Beamwidth (Rayleigh criterion): b Effective number of beams: N =W/b Frame Rate: FR

  15. Cardiac flow imaging: fo= 2 MHz, 15 mm aperture, beamwidth 3 mm 30 beams covers the left ventricle fc = 600 Hz ~ 0.21 m/sec. lower velocity limit Minimum detectable Doppler shift Clutter filter cutoff frequency: fc > N*FR (transit time effect mechanical scan) Frame rate FR =1 Hz FR = 10 Hz FR=20 Hz Width (# beams) N=30 30 Hz 300 Hz 600 Hz N=70 70 Hz 700 Hz 1400 Hz

  16. Reflected wave does not hit the transducer Max Dopplershift 600 Hz ~ 0.21 m/sec Color flow imaging with a mechanical probe v = W*FR

  17. Horten, Norway september 2001 GE-Vingmed closed down production line for CFM after 15 years of continuous production Atlanta, GA april 1986 Vingmed, introduced CFM The first commercial colorflow imaging scanner with mechanical probe

  18. Periferal vessel imaging with fo= 10 MHz Mechanical scanning: fc = 1400 Hz ~ 108 mm/sec. Minimum detectable Doppler shift Clutter filter cutoff frequency: fc > N*FR Frame rate FR =1 Hz FR = 10 Hz FR=20 Hz Width (# beams) N=30 30 Hz 300 Hz 600 Hz N=70 70 Hz 700 Hz 1400 Hz Electronic scanning: fc = 30 Hz ~ 2.3 mm/sec. Packet acquisition (P=10): Frame rate = 35 frames/sec Continuous acquisition: Frame rate = 350 frames/sec

  19. Combining tissue and flowContinuous sweep acquisition + Brachial artery

  20. Temporal averaging for mean frequency estimator k=1 : 4, uncorrelated signal packets Example: Effect of averaging R1 : Variance of angle(R1) reduced by factor 24! Effect of averaging angle(R1): Variance reduction factor=4

More Related