k-Wave User Forum » Topic: ultrasound simulation

k-Wave User Forum » Topic: ultrasound simulation http://www.k-wave.org/forum/topic/ultrasound-simulation-1 Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 03:13:52 +0000 http://bbpress.org/?v=1.0.2 <![CDATA[Search]]> q http://www.k-wave.org/forum/search.php Bradley Treeby on "ultrasound simulation" http://www.k-wave.org/forum/topic/ultrasound-simulation-1#post-5514 Thu, 26 May 2016 16:19:03 +0000 Bradley Treeby 5514@http://www.k-wave.org/forum/ Hi Swetha, The second peak that you see in the time domain traces comes from the edge wave. If you turn plotting on (set <code>'PlotSim', true</code>), you will see the part of the wave that I mean. If you remove the first part of the signal, it will be easier to see the reflection. The reflection has a very low amplitude due to geometrical spreading (the point reflector is a long way from the source). For example, after changing Nx to 512, try <code>plot(sensor_data(1, 1000:end).'</code>. Brad. ssg47 on "ultrasound simulation" http://www.k-wave.org/forum/topic/ultrasound-simulation-1#post-5508 Wed, 18 May 2016 13:50:36 +0000 ssg47 5508@http://www.k-wave.org/forum/ I also changed Nx from 128 to 512 because I want to simulate deep tissue imaging. But I don't get any echoes from the scatterers. I tried increasing the strength of the input signal as well but it doesn't produce any change. Is there something else I need to consider. Thank you so much for helping! ssg47 on "ultrasound simulation" http://www.k-wave.org/forum/topic/ultrasound-simulation-1#post-5505 Mon, 16 May 2016 19:28:36 +0000 ssg47 5505@http://www.k-wave.org/forum/ Hi Dr. Treeby, I made those changes and I think I see the delay at the end of the signal from sensor data. I was wondering what are the different impulse I see in the plotted signal(I don't know how to post an image here). I understand that the first part is the input signal to the source and the last part is the received echo. But there is a small signal between these two and I'm not sure I can explain it. It would be great if you could help me! <pre><code>clear all; pml_x_size = 20; pml_y_size = 20; % create the computational grid Nx = 128 - 2*pml_x_size; % number of grid points in the x (row) direction Ny = 96 - 2*pml_y_size; % number of grid points in the y (column) direction dx = 0.2e-3; % grid point spacing in the x direction [m] dy = 0.2e-3; % grid point spacing in the y direction [m] kgrid = makeGrid(Nx, dx, Ny, dy); gridx_pts =11; c0 = 1540; % [m/s] rho0 = 1000; % [kg/m^3] medium.alpha_coeff = 0.75; % [dB/(MHz^y cm)] medium.alpha_power = 1.5; medium.BonA = 6; medium.sound_speed_ref = 1540; % define the properties of the propagation medium t_end = (Nx*dx)*2.2/c0; % [s] %kgrid.t_array = makeTime(kgrid, c0, [], t_end); kgrid.t_array = 0e-9:15e-9:t_end; source_strength = 5e6; % [Pa] tone_burst_freq = 1.875e6; % [Hz] tone_burst_cycles = 5; % create the input signal using toneBurst input_signal = toneBurst(1/kgrid.dt, tone_burst_freq, tone_burst_cycles); %define the source source.p_mask = zeros(Nx,Ny); num_elements = 32; % [grid points] x_offset = 1; % [grid points] start_index = Ny/2 - round(num_elements/2) + 1; source.p_mask(x_offset, start_index:start_index + num_elements - 1) = 1; source.p = input_signal; % define the sensor sensor.mask = zeros(Nx,Ny); x_offset = 1; % [grid points] start_index = Ny/2 - round(num_elements/2) + 1; sensor.mask(x_offset, start_index) = 1; sensor.mask(x_offset,start_index+13) = 1; %define medium Ny_tot = Ny+gridx_pts; sound_speed_map = c0*ones(Nx, Ny_tot); density_map = rho0*ones(Nx, Ny_tot); cwire = 3000; scattering_rho0 = cwire/1.5;%1150 % define the fishing wire point as a ball (high scattering intensity) radius = 0.1e-3; % [m] scattering_region = makeCircle(Nx, Ny_tot, Nx-1,Ny_tot/2,radius,'true'); % assign scatterer the properties sound_speed_map(scattering_region == 1) = cwire; density_map(scattering_region == 1) = scattering_rho0; input_args = {'PMLInside', false, 'PMLSize', [pml_x_size, pml_y_size],'PlotSim',false,'PlotLayout',true,'PlotScale','auto'}; psn = 1; for i = 1:4 medium.sound_speed = sound_speed_map(:,psn:psn+Ny-1); medium.density = density_map(:,psn:psn+Ny-1); sensor_data = kspaceFirstOrder2D(kgrid, medium, source, sensor,input_args{:}); sdata(i,:,:) = sensor_data; psn = psn +2; end % plot the simulated sensor data figure; hold on; for i = 1:4 plot(reshape(sdata(i,1,:),[1,kgrid.Nt]));hold on end ylabel('Sensor Position'); xlabel('Time Step');</code></pre> Thanks, Swetha Bradley Treeby on "ultrasound simulation" http://www.k-wave.org/forum/topic/ultrasound-simulation-1#post-5504 Sun, 15 May 2016 16:03:12 +0000 Bradley Treeby 5504@http://www.k-wave.org/forum/ Hi ssg47, There are a few problems with your code: (1) You forgot to pass <code>input_args</code> to <code>kspaceFirstOrder2D</code>, which means the defaults are used instead. In particular, this means the PML is inside the grid, and so your source is within the PML. (2) You don't need to scale the source pressure by the impedance if you are using <code>source.p</code>. (3) The time step is likely too big for a stable simulation (see command line warning). You can find a discussion of the stability criteria in the k-Wave manual. Hope that helps, Brad. ssg47 on "ultrasound simulation" http://www.k-wave.org/forum/topic/ultrasound-simulation-1#post-5500 Fri, 13 May 2016 17:11:08 +0000 ssg47 5500@http://www.k-wave.org/forum/ Hi Dr. Cox and Dr. Treeby, My question is about sensor data that is received after moving the target. I read posts regarding delay but didn't get an answer. When I move medium I don't get any shift in the signal that I am supposed to see. Is there some internal mechanism that gets rid of the shift in the signals so that they start at time index 0 ? I urgently need help. I have tried everything after reading the posts and manual but haven't got lucky yet. I also tried the bmode linear transducer example but the received signal for each scan line is not shifted. Here is my code: clear all; pml_x_size = 20; pml_y_size = 20; % create the computational grid Nx = 128 - 2*pml_x_size; % number of grid points in the x (row) direction Ny = 96 - 2*pml_y_size; % number of grid points in the y (column) direction dx = 0.2e-3; % grid point spacing in the x direction [m] dy = 0.2e-3; % grid point spacing in the y direction [m] kgrid = makeGrid(Nx, dx, Ny, dy); gridx_pts =11; c0 = 1540; % [m/s] rho0 = 1000; % [kg/m^3] medium.alpha_coeff = 0.75; % [dB/(MHz^y cm)] medium.alpha_power = 1.5; medium.BonA = 6; medium.sound_speed_ref = 1540; % define the properties of the propagation medium t_end = (Nx*dx)*2.2/c0; % [s] kgrid.t_array = makeTime(kgrid, c0, [], t_end); source_strength = 5e6; % [Pa] tone_burst_freq = 1.875e6; % [Hz] tone_burst_cycles = 5; % create the input signal using toneBurst input_signal = toneBurst(1/kgrid.dt, tone_burst_freq, tone_burst_cycles); % scale the source magnitude by the source_strength divided by the % impedance (the source is assigned to the particle velocity) input_signal = (source_strength./(c0*rho0)).*input_signal; % %define the source source.p_mask = zeros(Nx,Ny); num_elements = 32; % [grid points] x_offset = 1; % [grid points] start_index = Ny/2 - round(num_elements/2) + 1; source.p_mask(x_offset, start_index:start_index + num_elements - 1) = 1; source.p = input_signal; % define the sensor sensor.mask = zeros(Nx,Ny); x_offset = 1; % [grid points] start_index = Ny/2 - round(num_elements/2) + 1; sensor.mask(x_offset, start_index) = 1; sensor.mask(x_offset,start_index+13) = 1; %define medium Ny_tot = Ny+gridx_pts; sound_speed_map = c0*ones(Nx, Ny_tot); density_map = rho0*ones(Nx, Ny_tot); cwire = 3000; scattering_rho0 = cwire/1.5;%1150 % define the fishing wire point as a ball (high scattering intensity) radius = 0.1e-3; % [m] scattering_region = makeCircle(Nx, Ny_tot, Nx-1,Ny_tot/2,radius,'true'); % assign scatterer the properties sound_speed_map(scattering_region == 1) = cwire; density_map(scattering_region == 1) = scattering_rho0; %% input_args = {'PMLInside', false, 'PMLSize', [pml_x_size, pml_y_size],'PlotSim',true,'PlotLayout',true,'PlotScale','auto'}; for i = 1:4 medium.sound_speed = sound_speed_map(:,i:i+Ny-1); medium.density = density_map(:,i:i+Ny-1); sensor_data = kspaceFirstOrder2D(kgrid, medium, source, sensor); sdata(i,:,:) = sensor_data; end %% ========================================================================= % VISUALISATION % ========================================================================= % plot the simulated sensor data figure; hold on; for i = 1:4 plot(reshape(sdata(i,2,:),[1,kgrid.Nt])) end colormap(getColorMap); ylabel('Sensor Position'); xlabel('Time Step'); colorbar;