Can anyone please explain to me how I can use Kspaceorder2D and pstdelastic2D simultaneously for the following example?
http://www.k-wave.org/documentation/example_us_beam_patterns.php
What should be the input for the pstdelastic2d case? Any code example for this type of study? Thanks
What do you mean by simultaneously? Note, the imaging examples are all in 3D to capture the out of plane effects. There are some general examples of how to use the pstdElastic2D code under the "Elastic Wave Propagation" heading.
Dr. Treeby, thanks for your reply. I added the wrong link in my post. Here is the original one:
http://www.k-wave.org/documentation/example_ewp_shear_wave_snells_law.php
It mentioned that The simulation is run twice, first using the fluid code kspaceFirstOrder2D, and then using the elastic code pstdElastic2D. I can see the separate example of pstdElastic2D code, but how can I use the outcome of kspaceFirstOrder2D as the input of pstdElastic2D code? Thanks
Dr. Treeby, thanks for your reply. I added the wrong link in my post. Here is the original one:
http://www.k-wave.org/documentation/example_ewp_shear_wave_snells_law.php
It mentioned that The simulation is run twice, first using the fluid code kspaceFirstOrder2D, and then using the elastic code pstdElastic2D. I can see the separate example of pstdElastic2D code, but how can I use the outcome of kspaceFirstOrder2D as the input of pstdElastic2D code? Thanks
If you open the example from within the MATLAB help browser, you can click to open and run the code.
Dr. Treeby, thanks I got it. I have another follow-up question. After completing the kspaceFirstOrder2D, the example cleared out the source and used the following line to redefine the medium:
clear source
source.s_mask = source_mask;
source.sxx = -source_strength*toneBurst(1/kgrid.dt, source_freq, source_cycles);
source.syy = source.sxx;
I am wondering what is the reason for that. Thanks
This is because the acoustic equation is formulated in terms of pressure and particle velocity (and acoustic density), while the elastic equation is formed in terms of stress and particle velocity, so the source must be set in terms of stress. In the parts of the domain where the shear speed is zero, the diagonal parts of the stress tensor are equal to the negative of the pressure (hence the code in the snippet you posted).
Thanks, I am trying to replicate this example for a linear array transducer which will act as a source as well as a sensor. The kspaceFirstOrder3D portion works fine as I used a transducer. input signal as the source. where
input_signal = (source_strength ./ (rho1 .* cp1)) *toneBurst(1/kgrid.dt, tone_burst_freq, tone_burst_cycles);
However for the pstdElastic3D simulation, I need to specify source.mask, source.sxx, and source.syy separately. For source Sxx, I am using -input signal=Sxx, but what should be the mask (source.mask) for transducer array? Thanks
I used transducer.active_elements_mask as source.s_mask as following. The simulation runs but, the stress value are very low that it doesn't show anything the plot. Here is the code for that:
input_signal = toneBurst(1/kgrid.dt, tone_burst_freq, tone_burst_cycles);
input_signal = (source_strength ./ (rho1 .* cp1)) .* input_signal;
source.s_mask = transducer.active_elements_mask;
source.sxx = -input_signal;
source.syy = source.sxx;
sensor_data_elastic = pstdElastic3D(kgrid, medium, source, sensor, input_args{:});
The inputs are in units of pressure (not particle velocity) so you can remove the scaling by the impedance (rho * c). Alternatively, also use a velocity source in the elastic code (instead of a stress source).
Dr. Treeby,
Thanks, I actually removed the (rho * c) term and found that I got the normal stress, but it can't track the shear stress at all. I will try with a velocity source in the elastic code (instead of a stress source) as per your suggestion.
Dr. Treeby, I tried with inserting velocity as input instead of stress, still, it can't track the shear stress. Am I supposed to get the similar result for velocity input instead of stress?
source.u_mask = sensor.mask;
source.ux=sensor_data_fluid.ux;
source.uy=sensor_data_fluid.uy;
source.uz=sensor_data_fluid.uz;
sensor_data_elastic = pstdElastic3D(kgrid, medium, source, sensor, input_args{:});
Also, I am not sure what to use for source. mask. I want to use the same transducer for both as a source of ARF and also for tracking. Can you please tell me a bit about selecting the source. u_mask/source.s_mask?
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