Method and apparatus for estimation and display of spectral broadening error margin for doppler time-velocity waveforms

• US 6,176,143 B1
• Filed: 12/01/1997
• Issued: 01/23/2001
• Est. Priority Date: 12/01/1997
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Otterson, Scott D., Mo, Larry Y. L.
• Primary Examiner(s): Fuller, Benjamin R.
• Assistant Examiner(s): THOMPSON, JEWEL VERGIE
• Application Number:
  US08/982,065
• Time in Patent Office: 1,149 Days
• Field of Search: 738/612.5, 600/454, 128/661.08
• US Class Current: 73/861.25
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00
• CPC Class Codes: A61B 8/488 involving Doppler signals
• CPC Class Codes: G01N 2291/02836 Flow rate, liquid level
• CPC Class Codes: G01P 21/025 for measuring speed of fluids; for measuring speed of bodies relative to fluids for measuring volume flow G01F25/10
• CPC Class Codes: G01P 5/244 involving pulsed waves

Abstract

A method of calibrating Doppler time-velocity waveforms obtained using a duplex ultrasound scanner. A spectral broadening error margin for the maximum velocity waveform is determined based on a unified theory of intrinsic spectral broadening for pulsed Doppler signals. The error margin is colorized or highlighted in the Doppler waveform display.

Claims

1. A method for displaying a spectral broadening error margin of a Doppler velocity-time waveform envelope, comprising the steps of:

transmitting pulses of ultrasound into a sample volume of ultrasound scatterers;

acquiring a multiplicity of successive samples of Doppler signals backscattered from said sample volume of ultrasound scatterers;

processing said Doppler signals to produce spectral line data representing velocity for continuous display of a succession of spectral lines during continuation of Doppler signal acquisition, the data for each spectral line comprising a multiplicity of frequency bins for different frequency intervals, each bin containing spectral power data for a respective frequency interval, the spectral power data in each bin for each spectral line being displayed as a scale in a respective pixel of a corresponding column of pixels on a display monitor;

for each spectral line, determining a spectral broadening error margin comprising errors due to bandwidth, diffraction and analysis time broadening; and

displaying a graphical representation of the magnitude of the determined spectral broadening error for each spectral line on said display monitor.

2. The method as defined in claim 1, wherein said processing step comprises taking Fast Fourier Transforms (FFTS) over a data window of samples, and wherein the spectral broadening error margin is determined in accordance with an equation:

$\mathrm{SBEM}=f_{\max }^{\mathrm{\prime <br><br>}}-\frac{f_{\max }^{\mathrm{\prime <br><br>}}-K_T/T_{\mathrm{FFT}}}{1+\left[c<br><br>\text{\hspace{1em}<br><br>}<br><br>K_L/\left(2<br><br>f_0<br><br>L\right)+K_W<br><br>\tan <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\theta <br><br>}/\left(2<br><br>F\right)\right]}$

where θ

is a beam-to-flow angle estimate;

L is a sample volume length;

K_L is a constant that depends on a shape of an axial sensitivity profile;

F is an effective F-number of a Doppler transmit-receive beamformer;

K_W is a constant that depends on a shape of a lateral sensitivity profile;

T_FFT is a duration of an FT data window; and

K_T is a constant that depends on a shape of said FT data window.

3. The method as defined in claim 1, wherein said step of displaying the determined spectral broadening error for each spectral line comprising highlighting a region below a Doppler velocity-time waveform envelope and corresponding to the determined spectral broadening error.

4. A system for displaying a spectral broadening error margin of a Doppler velocity-time waveform envelope, comprising:

means for transmitting pulses of ultrasound into a sample volume of ultrasound scatterers;

means for acquiring a multiplicity of successive samples of Doppler signals backscattered from said sample volume of ultrasound scatterers;

a display monitor comprising columns of pixels;

means for processing said Doppler signals to produce spectral line data representing velocity for continuous display of a succession of spectral lines during continuation of Doppler signal acquisition, the data for each spectral line comprising a multiplicity of frequency bins for different frequency intervals, each bin containing spectral power data for a respective frequency interval, the spectral power data in each bin for each spectral line being displayed as a scale in a respective pixel of a corresponding column of pixels on said display monitor;

means for determining a spectral broadening error margin for each spectral line, said spectral broadening error margin comprising errors due to bandwidth, diffraction and analysis time broadening; and

means for displaying a graphical representation of the magnitude of the determined spectral broadening error for each spectral line on said display monitor.

5. The system as defined in claim 4, wherein said means for displaying the determined spectral broadening error for each spectral line comprises means for high-lighting a region below a Doppler velocity-time waveform envelope and corresponding to the determined spectral broadening error.

6. A system for displaying a spectral broadening error margin of a Doppler velocity-time waveform envelope, comprising:

a Doppler transmit-receive beamformer comprising means for transmitting pulses of ultrasound into a sample volume of ultrasound scatterers and means for acquiring a multiplicity of successive samples of Doppler signals backscattered from said sample volume of ultrasound scatterers;

a display monitor comprising columns of pixels;

means for processing said Doppler signals to produce spectral line data representing velocity for continuous display of a succession of spectral lines during continuation of Doppler signal acquisition, the data for each spectral line comprising a multiplicity of frequency bins for different frequency intervals, each bin containing spectral power data for a respective frequency interval, the spectral power data in each bin for each spectral line being displayed as a scale in a respective pixel of a corresponding column of pixels on said display monitor;

means for determining a spectral broadening error margin for each spectral line, said spectral broadening error margin comprising errors due to bandwidth, diffraction and analysis time broadening; and

means for displaying a graphical representation of the magnitude of the determined spectral broadening error for each spectral line on said display monitor.

7. The system as defined in claim 6, wherein said processing means comprises a spectrum analyzer which takes Fast Fourier Transforms (FFTs) over a data window of samples, and the spectral broadening error margin is determined in accordance with an equation:

$\mathrm{SBEM}=f_{\max }^{\mathrm{\prime <br><br>}}-\frac{f_{\max }^{\mathrm{\prime <br><br>}}-K_T/T_{\mathrm{FFT}}}{1+\left[c<br><br>\text{\hspace{1em}<br><br>}<br><br>K_L/\left(2<br><br>f_0<br><br>L\right)+K_W<br><br>\tan <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\theta <br><br>}/\left(2<br><br>F\right)\right]}$

where θ

is a beam-to-flow angle estimate;

L is a sample volume length;

K_L is a constant that depends on a shape of an axial sensitivity profile;

F is the effective F-number of said Doppler transmit-receive beamformer;

K_W is a constant that depends on a shape of a lateral sensitivity profile;

T_FFT is the duration of said FT data window; and

K_T is a constant that depends on the shape of said FT data window.

8. The system as defined in claim 6, wherein said means for displaying the determined spectral broadening error for each spectral line comprise means for high-lighting a region below a Doppler velocity-time waveform envelope and corresponding to the determined spectral broadening error.

9. A system for displaying a spectral broadening error margin of a Doppler velocity-time waveform envelope, comprising:

a transducer comprising a multiplicity of ultrasound transducing elements;

a display monitor comprising a multiplicity of pixels;

a computer programmed to perform the following steps;

(a) controlling said transducer to transmit pulses of ultrasound into a sample volume of ultrasound scatterers;

(b) controlling said transducer to acquire a multiplicity of successive samples of Doppler signals backscattered from said sample volume of ultrasound scatterers;

(c) processing said Doppler signals to produce spectral line data representing velocity for continuous display of a succession of spectral lines during continuation of Doppler signal acquisition, the data for each spectral line comprising a multiplicity of frequency bins for different frequency intervals, each bin containing spectral power data for a respective frequency interval, the spectral power data in each bin for each spectral line being displayed as a scale in a respective pixel of a corresponding column of pixels on said display monitor;

(d) for each spectral line, determining a spectral broadening error margin comprising errors due to bandwidth, diffraction and analysis time broadening; and

(e) controlling said display monitor to display a graphical representation of the magnitude of the determined spectral broadening error for each spectral line.

10. The system as recited in claim 9, wherein said processing step comprises taking Fast Fourier Transforms (FFTs) over a data window of samples, and wherein the spectral broadening error margin is determined in accordance with an equation:

$\mathrm{SBEM}=f_{\max }^{\mathrm{\prime <br><br>}}-\frac{f_{\max }^{\mathrm{\prime <br><br>}}-K_T/T_{\mathrm{FFT}}}{1+\left[c<br><br>\text{\hspace{1em}<br><br>}<br><br>K_L/\left(2<br><br>f_0<br><br>L\right)+K_W<br><br>\tan <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\theta <br><br>}/\left(2<br><br>F\right)\right]}$

where θ

is a beam-to-flow angle estimate;

L is a sample volume length;

K_L is a constant that depends on a shape of an axial sensitivity profile;

F is an effective F-number for Doppler transmit-receive beamforming;

K_W is a constant that depends on a shape of a lateral sensitivity profile;

T_FFT is the duration of said data window; and

K_T is a constant that depends on a shape of said data window.

11. The system as recited in claim 9, wherein said step of displaying the determined spectral broadening error for each spectral line comprises highlighting a region below a Doppler velocity-time waveform envelope and corresponding to the determined spectral broadening error.