Exercise 3

Topic: Clutter-filter in ultrasound color-Doppler

You find the basis of the exercise in the article "Clutter Rejection Filters in Color Flow Imaging "

The topic is also described in "Waves...", chapter 10.3 E;     Background information

An example of an ultrasound signal from color-Doppler oppg3Data.mat

The file contains a complex demodulated IQ-signal for an image from a linear array probe.

Center frequency 7.5 MHz. It is transmitted 7 pulses for each beam, in total 66 beams. PRF=750Hz.

iq(k,r,b) is the IQ-signal for pulse k, range r, beam b.

The task is to design a filter that extracts the signal from moving blood and display it as a gray-scale image, beside the unfiltered signal. 

Remarks:

To save space iq is stored as a 16 bit integer. To convert iq to a floating-point number use the command:

iq=double(iq);

You can get the amplitude-image of the tissue-signal if you compute the power in each packet in the signal, for instance:

amp=10*log10(mean(abs(iq).^2);

Look at the real and imaginary part of the signal at a point in the image:

r=100;b=33;t=(0:6)/prf;

iq1=squeeze(iq(:,r,b));

plot(t,real(iq1),t,imag(iq1));

Use a high-pass filter on iq1 and plot the result.

Filter each point in the image and display the out-put signal power as a (logarithmic) gray-scale image.