![Page 1: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/1.jpg)
Chapter 8: Color and Spectral Doppler
![Page 2: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/2.jpg)
![Page 3: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/3.jpg)
![Page 4: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/4.jpg)
![Page 5: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/5.jpg)
![Page 6: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/6.jpg)
![Page 7: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/7.jpg)
![Page 8: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/8.jpg)
![Page 9: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/9.jpg)
![Page 10: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/10.jpg)
![Page 11: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/11.jpg)
Doppler Effect
![Page 12: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/12.jpg)
Doppler Effect
![Page 13: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/13.jpg)
Doppler Principles
• Relative motion of the source causes a change in received frequency.
• Blood flow velocity is measured by detecting Doppler frequency shifts.
receiver receiver source
![Page 14: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/14.jpg)
Doppler Principles
• When both source and receiver are stationary:
• When source is stationary and receiver is moving:
![Page 15: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/15.jpg)
Doppler Principles
• When receiver is stationary and source is moving:
![Page 16: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/16.jpg)
Doppler Equations
![Page 17: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/17.jpg)
Doppler Ultrasound
• Primary scattering site: red blood cell. The platelet is too small and the number of leukocytes is not significant.
• The red blood cell size is around several microns. Thus, scattering and speckle are also present.
• The red blood cells in a sample volume are assumed to move in unison.
![Page 18: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/18.jpg)
Doppler Equations
• Typical physiological flows (5-10m/sec at most) are much slower than sound velocity in the body (~1500m/sec).
• Doppler shift is doubled due to round-trip propagation. • Only parallel flows can be detected.
v
c
θ
![Page 19: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/19.jpg)
Flow Pattern v. Velocity Profile
velocity or Doppler shift
0
ultrasound beam
![Page 20: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/20.jpg)
Flow Pattern v. Velocity Profile
velocity or Doppler shift
0
ultrasound beam
![Page 21: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/21.jpg)
Flow Pattern v. Velocity Profile
velocity or Doppler shift
0
ultrasound beam
![Page 22: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/22.jpg)
Doppler Spectrum Estimation
• Short-time Fourier transform (Spectral Doppler).
• Correlation based estimation (Color Doppler).
fs fd fs+fd
original Doppler shifted demodulated
![Page 23: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/23.jpg)
Blood Flow Measurements
• Short Time Fourier Analysis: PW,CW, Audio Doppler.
• Correlation processing: Color Doppler, Doppler Power, Doppler Energy, Convergent Color Doppler.
• Tracking. • Correlation Analysis.
![Page 24: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/24.jpg)
Continuous Wave (CW) Doppler T R
time
velo
city
time
Received signal
![Page 25: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/25.jpg)
CW Doppler CW
oscillator
CW transmitter
T R
amplifier
demodulator
filter spectral
estimation
audio conversion
display speaker
signal processing
![Page 26: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/26.jpg)
CW Doppler
• Array CW and AUX CW (half transmit, half receive).
• Mainly for Cardiology. • Good velocity (frequency) resolution. • No range resolution. Flows along the same
direction are all detected. • Frequency downshift due to attenuation can be
ignored.
![Page 27: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/27.jpg)
CW Doppler Processing
f0 -f0 f0+fd -f0-fd
fd -2f0-fd
fd
original spectrum
demodulated
demodulated and filtered
![Page 28: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/28.jpg)
Wall Filter (Clutter Filter)
time
velo
city
![Page 29: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/29.jpg)
CW Doppler Processing
• Time-interval histogram. • 32-128 pt FFT. • Model-based spectrum estimation (AR),
time-frequency analysis. • Magnitudes are converted in dB and
displayed. • Post-processing similar to B-mode.
![Page 30: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/30.jpg)
Audio Doppler
• For typical blood velocities and carrier frequencies, the Doppler shifts from blood happen to be in the human audible range (near DC to 20KHz).
• Positive shifts in one channel and negative ones in the other.
• Hilbert transform. • Clinically useful.
Right
Left
![Page 31: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/31.jpg)
• CW: No range resolution. • Sampling in time = sampling in range. à CW Doppler to PW Doppler.
CW à PW
![Page 32: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/32.jpg)
Pulsed Wave (PW) Doppler
time
PRI
![Page 33: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/33.jpg)
Another View for PW Doppler,…
![Page 34: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/34.jpg)
Autocorrelation Processing
取自www.acuson.com
S(t)
PRI (Pulse Repetition Interval)
Autocorrelation function:
![Page 35: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/35.jpg)
PW System Diagram
CW oscillator
PW transmitter (gated CW)
transducer amplifier
demod./LPF
filter spectral estimation
audio conversion
display speaker
signal processing
gating
sample&hold
![Page 36: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/36.jpg)
Pulsed Wave (PW) Doppler
time
PRI
![Page 37: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/37.jpg)
Velocity Ambiguity
vmax
no aliasing
vmax -vmax
aliasing
![Page 38: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/38.jpg)
Velocity Ambiguity (no aliasing)
![Page 39: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/39.jpg)
Velocity Ambiguity (with aliasing)
![Page 40: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/40.jpg)
Range Ambiguity
PRI
![Page 41: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/41.jpg)
Range Ambiguity
PRI T0
OR ?
![Page 42: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/42.jpg)
Pulse Wave (PW) Doppler
• Pulse-echo method, similar to B-mode. • Post-processing similar to CW. • Adjustable range resolution (gate). • Maximum detectable velocity is λ/(4*PRI). • Maximum depth is (c*PRI)/2. • 32-128 point FFT.
![Page 43: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/43.jpg)
PW Blood Flow Measurements 取自www.acuson.com
S(t)
PRI (Pulse Repetition Interval)
![Page 44: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/44.jpg)
• Single gate à multiple gates. • Local flow information à 2D flow
information. • Less time for velocity estimation:
quantitative à qualitative.
PW à Color Doppler
![Page 45: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/45.jpg)
Color Doppler Parameters
• Use efficient time domain correlation techniques to calculate flow characteristics.
• Auto-correlation of the Doppler signal. • Commonly derived parameters are mean velocity
(including directionality), variance and energy (power).
f
![Page 46: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/46.jpg)
Color Doppler
multiple firings
multiple gates
![Page 47: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/47.jpg)
Color Doppler
multiple firings
multiple gates
![Page 48: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/48.jpg)
Color Doppler
• Similar to B-mode, except that each line is fired multiple times (5-15).
• Correlation processing. • Multiple range gates along each line. • Real-time two-dimensional flow imaging. • Poor velocity (frequency) resolution.
![Page 49: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/49.jpg)
Color Doppler Derivation: Mean Velocity
![Page 50: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/50.jpg)
Color Doppler Derivation: Mean Velocity
: even : odd
![Page 51: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/51.jpg)
In practice, R(t) is by definition a discrete signal,…
![Page 52: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/52.jpg)
Color Doppler Derivation: Mean Velocity
• For a single scatterer:
• The flow direction is determined by the sign of the mean frequency.
![Page 53: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/53.jpg)
Color Doppler Derivation: Variance
![Page 54: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/54.jpg)
Color Doppler Derivation: Variance
![Page 55: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/55.jpg)
Color Doppler Derivation: Energy
f
![Page 56: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/56.jpg)
Color Doppler
• Flow parameters are mapped into colors for display (1D or 2D).
• Choice of map affects the presentation of Color Doppler images.
![Page 57: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/57.jpg)
Color Doppler: Signal Processing
beam former
high pass filter
auto-correlator
parameter estimator
signal and display processor
• Significant frame rate reduction. • Small color boxes are often used to increase
frame rate. • Sophisticated systems utilize multiple beam
formation to further increase frame rate.
![Page 58: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/58.jpg)
Doppler: Complications
• Non-trivial wall filters are required to remove interference from slow-moving objects.
• Adequate signal processing capabilities and sufficient dynamic range are necessary to detect weak flows.
• Conflicts with frame rate requirements. • Only parallel flow is detectable.
![Page 60: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/60.jpg)
• Load hw3_dat.mat. In this data file, DopplerData represents a PW Doppler data set. The size of the data is 128 X 400, representing gated received data with 128 firings and 400 data samples for each firing. In the same data file, the following parameters are also included:
– PRI: pulse repetition interval in usec. – fs: sampling frequency in MHz. – f0: center frequency of the transmitted pulse in
MHz.
![Page 61: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/61.jpg)
• For each firing, perform the following processing. The total number of samples will reduce from 400 to a single complex sample after the processing. Repeat the processing for all firings in order to obtain 128 complex samples.
demodulation low pass filtering summing
![Page 62: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/62.jpg)
1. Based on the 128 complex samples, calculate the velocity profile using FFT. The profile should be plotted on a logarithmic scale with a 40dB range. The horizontal axis should also be labeled with proper velocity scale. (30%)
![Page 63: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/63.jpg)
2. Re-do Problem 1 by using only the even samples. Also re-do Problem 1, by using only the first 200 RF data points during the summation. Explain your results. (30%)
![Page 64: Chapter 8: Color and Spectral Dopplercc.ee.ntu.edu.tw/~ultrasound/classnotes/us1/CHAPTER8.pdf · Color Doppler: Signal Processing beam former high pass filter auto-correlator parameter](https://reader035.vdocuments.net/reader035/viewer/2022062317/5ecb00d992f2e611c80426d0/html5/thumbnails/64.jpg)
3. Based on the original complex samples, calculate and plot the mean velocity, variance and energy as the number of samples increases from 2 to 128. Also compare with the results when only using the center 100 (151:250) points for the summing. Note that the discrete correlation function is defined as the following (40%).
4. (bonus) Explore any related Doppler issues based on the dataset.