Ultrasound Doppler Doppler Modes Spectral Doppler Color Flow Imaging Velocity/freq - time...

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Transcript of Ultrasound Doppler Doppler Modes Spectral Doppler Color Flow Imaging Velocity/freq - time...

  • Rad225/Bioe225

    Ultrasound

    Fall 2019

    Doppler Modes Spectral Doppler Color Flow Imaging

    ✤Velocity/freq - time spectrogram ✤Quantitative analysis

    ✤2D image of flow field ✤Qualitative visualization

    Continuous Wave

    Pulsed Wave

    Color Flow Power

    Very high velocities

    No depth resolution

    Max velocity limit

    Sample Gate Control

    Mean velocity

    Angle dependent

  • Rad225/Bioe225

    Ultrasound

    Fall 2019Color Doppler

    B-mode image Subset of B-mode image is displayed in color mode Color overlay of the velocity

    Toward transducer is in upper color, away in lower color

  • Rad225/Bioe225

    Ultrasound

    Fall 2019Simple Description

    Interrogate each line 8-10 times. Compare. “Stationary stuff subtracts out.”

    • Stationary stuff stays the same • Moving stuff changes

  • Rad225/Bioe225

    Ultrasound

    Fall 2019Phase Shift Autocorrelation

    Interrogate each line 8-10 times. Looking at the change in the phase of the signals from one transmit pulse to the next. The phase autocorrelation is used to form an average Doppler frequency.

  • Rad225/Bioe225

    Ultrasound

    Fall 2019Doppler Angle Effects

    Low frequency Doppler signals removed by wall filter

    Steady flow phantom

  • Rad225/Bioe225

    Ultrasound

    Fall 2019Doppler - Beam Angling

  • Rad225/Bioe225

    Ultrasound

    Fall 2019Doppler - Beam Angling

  • Rad225/Bioe225

    Ultrasound

    Fall 2019Doppler Angle Effects

    Steady flow phantom

    Aliasing

  • Rad225/Bioe225

    Ultrasound

    Fall 2019Doppler - Color Flow

    • Uses multiple gates - allows velocity measurements in many locations.

    • But only measure a mean in each location - fewer measurements/location.

    • Overlay a color on a greyscale image.

  • Rad225/Bioe225

    Ultrasound

    Fall 2019Color Flow of Ureter Jets

  • Rad225/Bioe225

    Ultrasound

    Fall 2019Color Flow of Ureter Jets

  • Rad225/Bioe225

    Ultrasound

    Fall 2019Frame Rate Considerations

    Interrogate each line 8-10 times.

  • Rad225/Bioe225

    Ultrasound

    Fall 2019What happens when transducer is rotated?

    Need to be careful of how to hold the transducer.

  • Rad225/Bioe225

    Ultrasound

    Fall 2019Wall Filter

  • Rad225/Bioe225

    Ultrasound

    Fall 2019

    Doppler Modes Spectral Doppler Color Flow Imaging

    ✤Velocity/freq - time spectrogram ✤Quantitative analysis

    ✤2D image of flow field ✤Qualitative visualization

    Continuous Wave

    Pulsed Wave

    Color Flow Power

    Very high velocities

    No depth resolution

    Max velocity limit

    Sample Gate Control

    Mean velocity

    Angle dependent

    Signal amplitude

    Angle independent

  • Rad225/Bioe225

    Ultrasound

    Fall 2019Power

    • Anywhere where there is a measurable velocity, encode the image with color. The color depends on the amplitude(strength) of the Doppler signal.

    • More sensitive than color flow, even at low angles.

    • Aliasing doesn’t affect display.

  • Rad225/Bioe225

    Ultrasound

    Fall 2019

    Color Flow

    Signal Magnitude

    Velocity

    Color Flow Color Overlay

    Power Color Overlay

  • Rad225/Bioe225

    Ultrasound

    Fall 2019

    Color Flow

    Signal Magnitude

    Velocity

    Color Flow Color Overlay

    displays velocity

    Where velocity is over a threshhold,

  • Rad225/Bioe225

    Ultrasound

    Fall 2019

    Power

    Signal Magnitude

    Velocity

    Color Flow Color Overlay

    Power Color Overlay

    Where velocity is over a threshhold, displays Doppler signal magnitude

  • Rad225/Bioe225

    Ultrasound

    Fall 2019Color Flow vs Power

  • Rad225/Bioe225

    Ultrasound

    Fall 2019Power Doppler • Any measurable velocity is encoded with color. The color depends on the amplitude of the doppler signal. • More sensitive than color flow (not clear why, potentially due to frame averaging).

  • Rad225/Bioe225

    Ultrasound

    Fall 2019Color Flow vs Power

  • Rad225/Bioe225

    Ultrasound

    Fall 2019Color Flow vs Power

  • Rad225/Bioe225

    Ultrasound

    Fall 2019

    What kind of Doppler image?

    Why is the structure indicated by the dashed arrow not colored?

    Why is the structure indicated by the green arrow not colored?

  • Rad225/Bioe225

    Ultrasound

    Fall 2019

    fUS imaging relies on ultrafast imaging scanners that are able to acquire images at thousands of frames per second. Instead of the line per line acquisition of conventional ultrasound devices, ultrafast ultrasound takes advantage of successive tilted plane wave transmissions that are afterward coherently compounded to form images at high frame rates.