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Insana Lab: Ultrasonic Imaging - The University of Illinois at Urbana-Champaign

Insana Lab: Ultrasound Research Interface (URI)

Spectral Doppler

Spectral Doppler imaging displays the Doppler spectrum (sonogram) of the RF data. The spread of flow information within the Doppler range gate is displayed as grayscale intensities on a time vs velocity plot.
Currently URI-OPT supports RF data collected in the URI D-only (full-screen D, D-Liv/B-Frz) and B-live/D-live modes. Due to Matlab limitations, the program may takes a long time to process a large D-mode file (>40MB), and may run into memory overflow problem.

To run the spectral Doppler program in Matlab:
>> URIDmode

You should see a window similar to this:

(Move cursor over the fields in this picture to see short descriptions,
or click on them to see full explanations.)

Select an RF data file by pressing the "Browse" button at the upper right corner.
If you selected an URI file, then the parameters like frequency and PRF and vector numbers will be automatically loaded.
Now you can manually adjust the parameters in all fields.
Then press "OK" button. The Matlab command window will display this message:

Processing......

Do not click on the GUI window while Matlab is processing, or images may be displayed incorrectly.

When process is finished,
If the data was acquired in D-only mode, a single figure with the Doppler spectrum will be displayed:

6 cardiac cycles of spectral Doppler data acquired at carotid artery

If the data was acquired in D-Liv/B-liv combined mode, an additional figure will display the B-mode (automatically scan-converted, if necessary) image with indicator of Doppler gate location.

B-mode image of URI BD data acquired at carotid artery

For more information, please also look at the function URIDmodeF.m on how spectral Doppler mode is processed in URI-OPT.
URIDmodeF.m is the functional form of URIDmode.m. It does not use graphical-user-interface, but is convenient for user to modify and test out new codes.

Color M-mode

If the "display as CM mode" box has been checked, then URIDmode will display Color M-mode images instead of spectral Doppler displays.
When the CM mode box is checked, most of the parameters are similar to those in URICBmode: the three threshold fields become modifiable, the available filter types are also slightly different from those in spectral Doppler analysis.
When processed, the flow estimation is color-mapped on the grayscale log-compressed envelope of the echo data, displayed against time. Since Doppler data are used here for both flow estimation and M-display, the background is actually generated using the narrowband RF instead of broadband normally used in M-mode.
For example, the following CM image is generated using the same RF data used for the above spectral Doppler display, except the whole data range is used instead of only the range gate.

CM-mode image generated using Doppler data acquired at carotid artery.

Parameters and Buttons in the Color Doppler GUI

File Path
The path name of the RF data file being processed.
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File Name
The filename of the RF data file being processed.
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Browse Button
Press this button to select other RF data files.
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Information of selected URI data
This field is blank at first, but appears after a file has been selected with the "Browse" button.
It shows the imaging mode (D, BD, etc) the data were acquired in. top

Frame Number
Select a single frame from the RF data file. The total avaible number of frames is displayed in parenthesis.
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Range gate start
Starting location of the rangegate in samples.
Sample instead of cm is used to prevent errors in non-URI data collected with different sampling rate.
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Range gate size
Doppler range gate size in samples.
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First Vector Number
Starting vector number of the data used.
Default is 1. User can enter a value larger than 1 to select a smaller portion of data to be processed.
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Last Vector Number
Ending vector number of data used. Enter 0 for all. Default is the available number of vectors. User can enter a value smaller than the default to select a smaller portion of data to be processed.
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Center frequency
Transmitted center frequency in MHz.
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PRF
Pulse repetition frequency in Hertz.
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CMcheckbox
Check this box to display Color M-mode image instead of spectral Doppler.
This will activate the following three threshold fields.
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Tissue Threshold
For CM-mode only.
Stationary tissue often has higher intensity than flowing blood, so the objects with higher pre-wallfiltered signal amplitude in the image usually suggests stationary tissue.
Increasing tissue threshold allows fewer samples to be mapped with color; decreasing tissue threshold allows more samples to be colormapped.
Enter 0 to skip this step.
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Clutter Threshold
For CM-mode only.
The power of each post-wallfiltered sample has to exceed ClutterThreshold to be designated as non-stationary and non-noise.
Similar to "gain" in color mode.
Enter 0 to skip this step.
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Velocity Threshold
For CM-mode only.
Velocity estimation has to exceed this threshold to be colormapped.
Enter 0 to skip this step.
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EnsembleSize
Number of vectors needed to generate a single line of spectrum.
Decreasing this value will blur the Doppler spectrums in the axial (velocity) direction.
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OverlapSize
How many vectors are reused for the generating the next line of spectrum.
Overlap size has to be smaller than Ensemble Size.
Decreasing this value will lower the resolution of the Doppler spectrums in the lateral (slow time) direction.
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FFTSize
Fourier Transform window size.
This should be equal or larger than Ensemble Size, so zero-padding can be done.
Decreasing this value will lower the resolution of the Doppler spectrums in the axial (velocity) direction.
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Wall Filter Type
Select the type of wall filter to be used.
Available options: no filter, IIR, regression, RMS butterworth, RMS chebyshev, eigen.
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Wall Filter Order
The order of the wall filter.
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Filter Frequency Cutoff
The cutoff frequency for IIR, RMS butterworth, or RMS chebyshev filters.
This value is a fraction of the center frequency. This number times the center frequency in MHz give the cutoff frequency in MHz.
This parameter is not used for regression or eigen filters.
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Chebyshev Filter Passband Ripple
The passband ripple for RMS Chebyshev filter.
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Baseline
amount to shift (between -0.5 to 0.5) to avoid the aliasing.
Negative amount lower the zero baseline to bottom half of the displayed spectrum; positive amount raise the zero baseline to top half.
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Doppler Angle
Doppler angle (in degrees) for velocity compensation. The velocity axis is increased by a division of cos(UserInput.DopplerAngle/180*pi). top

Smoothing gate
Smoothing methods used for color flow display: none, 2D median filter, weighted spatial 2D averaging.
Select smoothing window size in samples: axial depth by lateral width.
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OK button
Start processing with the input parameters.
Do not press repeatedly while program is running.
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Quit button
Close GUI and clear figure handles.
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Close other figures
Close all other Matlab figures except this GUI. It does not affect the variables in workspace.
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