k-Wave User Forum » Topic: Trying to Model a single element US with a frequency of 10 MHz

k-Wave User Forum » Topic: Trying to Model a single element US with a frequency of 10 MHz http://www.k-wave.org/forum/topic/trying-to-model-a-single-element-us-with-a-frequency-of-10-mhz Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 14:19:28 +0000 http://bbpress.org/?v=1.0.2 <![CDATA[Search]]> q http://www.k-wave.org/forum/search.php Bradley Treeby on "Trying to Model a single element US with a frequency of 10 MHz" http://www.k-wave.org/forum/topic/trying-to-model-a-single-element-us-with-a-frequency-of-10-mhz#post-6841 Wed, 10 Apr 2019 13:48:07 +0000 Bradley Treeby 6841@http://www.k-wave.org/forum/ Hi douavang96, The scatterer is very small compared to the wavelength, and the contrast is reasonably weak. My guess is that it's just acoustically transparent within the accuracy of the simulation (governed by the accuracy of the PML). What if you try increasing the size of the scatterer relative to the wavelength, or increasing the contrast? Brad. douavang96 on "Trying to Model a single element US with a frequency of 10 MHz" http://www.k-wave.org/forum/topic/trying-to-model-a-single-element-us-with-a-frequency-of-10-mhz#post-6828 Mon, 08 Apr 2019 18:43:30 +0000 douavang96 6828@http://www.k-wave.org/forum/ Hello, I am using the ultrasound B-Mode images example as a base to create my simulation. I have a single point transducer with multiple point targets. I have successfully simulated a situation with a input signal of 1 MHz with the grid size in the 100 um scale. However, I am not getting the same good results when I change the input signal to 10 MHz. Meaning the received input signal may not be the frequency i set and I am not getting any reflected signal. I have modified the grid size, smaller grid size, to allow for a larger maximum allowed frequency. My code is below and any help is appreciated. %% Initialization clearvars; % simulation settings DATA_CAST = 'single'; %% ========================================================================= % DEFINE THE K-WAVE GRID % ========================================================================= % set the size of the perfectly matched layer (PML) PML_X_SIZE = 10; % [grid points] PML_Y_SIZE = 10; % [grid points] PML_Z_SIZE = 10; % [grid points] % set total number of grid points not including the PML gp = 64; Nx = gp - 2*PML_X_SIZE; % [grid points] Ny = gp - 2*PML_Y_SIZE; % [grid points] Nz = gp - 2*PML_Z_SIZE; % [grid points] % set desired grid size in the x-direction not including the PML x = Nx*1e-5; % [m] % calculate the spacing between the grid points dx = x/Nx; % [m] dy = dx; % [m] dz = dx; % [m] % create the k-space grid kgrid = kWaveGrid(Nx, dx, Ny, dy, Nz, dz); %% ========================================================================= % DEFINE THE MEDIUM PARAMETERS % ========================================================================= % define the properties of the propagation medium 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; % create the time array t_end = (Nx * dx) * 2.4 / c0; % [s] kgrid.makeTime(c0, [], t_end); % fs =100e6; % dt = 1/fs; % Nt = round(t_end/dt); % kgrid.setTime(Nt, dt) % ========================================================================= % define a large image size to move across Nx_tot = Nx; Ny_tot = Ny; Nz_tot = Nz; %% ========================================================================= % DEFINE THE INPUT SIGNAL % ========================================================================= % define properties of the input signal source_strength = .1e6; % [Pa] tone_burst_freq = 10e6; % [Hz] tone_burst_cycles = 1; % create the input signal using toneBurst input_signal = toneBurst(1/kgrid.dt, tone_burst_freq, tone_burst_cycles,'Plot',true,'SignalLength',20); % 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 ULTRASOUND TRANSDUCER % ========================================================================= % physical properties of the transducer transducer.number_elements = 1; % total number of transducer elements transducer.element_width = 1; % width of each element [grid points] transducer.element_length = 1; % length of each element [grid points] transducer.element_spacing = 0; % spacing (kerf width) between the elements [grid points] transducer.radius = inf; % radius of curvature of the transducer [m] % transducer.radius = 20e-3; % radius of curvature of the transducer [m] % calculate the width of the transducer in grid points transducer_width = transducer.number_elements * transducer.element_width ... + (transducer.number_elements - 1) * transducer.element_spacing; % use this to position the transducer in the middle of the computational grid transducer.position = round([1, Ny/2 - transducer_width/2, Nz/2 - transducer.element_length/2]); % properties used to derive the beamforming delays transducer.sound_speed = c0; % sound speed [m/s] focus = x*10; transducer.focus_distance = focus; % focus distance [m] transducer.elevation_focus_distance = focus; % focus distance in the elevation plane [m] transducer.steering_angle = 0; % steering angle [degrees] % define the transducer elements that are currently active number_active_elements = 1; transducer.active_elements = ones(transducer.number_elements, 1); % append input signal used to drive the transducer transducer.input_signal = input_signal; % create the transducer using the defined settings transducer = kWaveTransducer(kgrid, transducer); % print out transducer properties %transducer.properties; %% run the simulation % set the input settings input_args = {... 'PMLInside', false, 'PMLSize', [PML_X_SIZE, PML_Y_SIZE, PML_Z_SIZE], ... 'DataCast', DATA_CAST, 'DataRecast', true, 'PlotSim', true}; % scattering_region3 = zeros(Nx_tot,Ny_tot,Nz_tot); % sound_speed_map = c0 * ones(Nx_tot, Ny_tot, Nz_tot); % density_map = rho0 * ones(Nx_tot, Ny_tot, Nz_tot); % medium.sound_speed = sound_speed_map; % medium.density = density_map; % % sensor_blank = kspaceFirstOrder3D(kgrid, medium, transducer, transducer, input_args{:}); % figure;plot(kgrid.t_array,sensor_blank) % title('Blank Data') % xlabel('time (s)'),ylabel('recorded pressure'); % sensor_data(i+3,:) = kspaceFirstOrder3D(kgrid, medium, transducer, transducer, input_args{:}); n = 1; maxLine = 1; for i= 1:maxLine scattering_region3 = zeros(Nx_tot,Ny_tot,Nz_tot); scattering_region3(10, Ny/2+(i-(maxLine+1)/2), Nz/2) = 1; scattering_region3(20, Ny/2+(i-(maxLine+1)/2), Nz/2) = 1; % scattering_region3(30, Ny/2+(i-(maxLine+1)/2), Nz/2) = 1; % scattering_region3(Nx, Ny/2+(i-(maxLine+1)/2), Nz/2) = 1; sound_speed_map = c0 * ones(Nx_tot, Ny_tot, Nz_tot); density_map = rho0 * ones(Nx_tot, Ny_tot, Nz_tot); sound_speed_map(scattering_region3 == 1) = 1600; density_map(scattering_region3 == 1) = 1200; medium.sound_speed = sound_speed_map; medium.density = density_map; sensor_data(n,:) = kspaceFirstOrder3D(kgrid, medium, transducer, transducer, input_args{:}); n = n+1; % % test sensor % sensor.mask = scattering_region3; % sensor_data = kspaceFirstOrder3D(kgrid, medium, transducer, sensor, input_args{:}); end %% figure plot(kgrid.t_array,sensor_data);%ylim([-50 50]); title('Sensor Data') xlabel('time (s)'),ylabel('recorded pressure');%ylim(1e4*[-1.2 1.2]) %% ========================================================================= % PROCESS THE RESULTS % ========================================================================= % ----------------------------- % Remove Input Signal % ----------------------------- % create a window to set the first part of each scan line to zero to remove % interference from the input signal scan_line_win = getWin(kgrid.Nt * 2, 'Tukey', 'Param', 0.05).'; scan_line_win = [zeros(1, round(length(input_signal) * 2)),... scan_line_win(1:end/2 - round(length(input_signal) * 2))]; % apply the window to each of the scan lines scan_line1 = bsxfun(@times, scan_line_win, sensor_data); figure plot(kgrid.t_array,scan_line1) title('Scan Line1') xlabel('time (s)');ylabel('Pressure');