Post on 05-Aug-2020
Rad225/Bioe225
Ultrasound
Fall 2019
Doppler ModesSpectral 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 imageSubset of B-mode image is displayed in color modeColor 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 ModesSpectral 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.