I work on blood mimicking fluid and I tried to raise the density of water by dissolving NaCl in it (3.5g/1000g). When I tested it with a Doppler ultrasound device I found quite a nice flow signal. Is it possible that pure solution scatters ultrasound due to some acoustic impedance fluctuation of the solution or maybe it originates from some contamination in the NaCl?
Jakub:
There is one other example of a change in density of a fluid causing ultrasound echoes on both B-Mode and Color Doppler Modes that I am aware of: ureteral jets. When performing an US of the bladder trigone, jets of urine entering from the ureters can be identified. This effect is even more apparent on color doppler, which is interesting as I believe that the color doppler phenomenon relies on red blood cell movement in relation to the ultrasound probe. Prior studies examining the finding of ureteral jets have theorized that a difference in density between the urine in the ureter and the urine in the bladder is responsible for the US appearance. So my guess regarding what you observed with your experiment was that the NaCl was not contaminated, but rather the interaction between different densities of saline resulted in the ultrasonographic findings.
I hope that helps
Ralph
If your solution has moving scatterers, you should get a Doppler signal. This may be undissolved portion of your solution, small bubbles, impurities, and can be the effect of dense solution having large particles caught by ultrasound as scatterers. If you can measure the size of solution particles and compare to ultrasound wavelength that will give you an idea.
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