k-Wave User Forum » Topic: 1D Linear Probe Beam Simulation – Ultrasound Pulse Gradually Disappearing

k-Wave User Forum » Topic: 1D Linear Probe Beam Simulation – Ultrasound Pulse Gradually Disappearing http://www.k-wave.org/forum/topic/1d-linear-probe-beam-simulation-%e2%80%93-ultrasound-pulse-gradually-disappearing Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 01:11:34 +0000 http://bbpress.org/?v=1.0.2 <![CDATA[Search]]> q http://www.k-wave.org/forum/search.php Gwansuk on "1D Linear Probe Beam Simulation – Ultrasound Pulse Gradually Disappearing" http://www.k-wave.org/forum/topic/1d-linear-probe-beam-simulation-%e2%80%93-ultrasound-pulse-gradually-disappearing#post-9190 Wed, 26 Feb 2025 08:23:51 +0000 Gwansuk 9190@http://www.k-wave.org/forum/ Hello, I am currently simulating the acoustic field of a 1D linear probe using k-Wave. I have modified the code based on example_us_beam_patterns.m, and my key simulation settings are as follows: Frequency: 5 MHz Grid spacing (dx): 0.025e-3 m I confirmed that the initial ultrasound pulse propagates correctly. However, the pressure at the focal region is extremely low in the simulation results, making the beam pattern nearly invisible. It appears as if the ultrasound wave propagates and then disappears. Does anyone have any insights or suggestions on why this might be happening? I would appreciate any insights or suggestions on how to resolve this issue. Thank you! Gwansuk Below is the complete code: clearvars; % simulation settings DATA_CAST = 'gpuArray-single'; % set to 'single' or 'gpuArray-single' to speed up computations MASK_PLANE = 'xy'; % set to 'xy' or 'xz' to generate the beam pattern in different planes USE_STATISTICS = true; % set to true to compute the rms or peak beam patterns, set to false to compute the harmonic beam patterns % ========================================================================= % DEFINE THE K-WAVE GRID % ========================================================================= % set the size of the perfectly matched layer (PML) PML_X_SIZE = 20; % [grid points] PML_Y_SIZE = 10; % [grid points] PML_Z_SIZE = 10; % [grid points] % set total number of grid points not including the PML Nx = 84 - 2 * PML_X_SIZE; % [grid points] Ny = 64 - 2 * PML_Y_SIZE; % [grid points] Nz = 64 - 2 * PML_Z_SIZE; % [grid points] Nx = Nx * 74; %Nx = Nx * 74; Ny = Ny * 24; Nz = Nz * 1; % calculate the spacing between the grid points dx = 0.025e-3; % [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 medium.sound_speed = 1540; % [m/s] medium.density = 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 fs = 300e6; % Sampling rate (Hz) dt = 1/fs; % Time step (s) t_end = 80e-6; % Total simulation time (s) Nt = round(t_end / dt); % Number of time steps % Set time axis kgrid.t_array = 0:dt:(Nt-1)*dt; % ========================================================================= % DEFINE THE INPUT SIGNAL % ========================================================================= % define properties of the input signal source_strength = 1e6; % [Pa] tone_burst_freq = 5.0e6; % [Hz] tone_burst_cycles = 3; % 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 ./ (medium.sound_speed * medium.density)) .* input_signal; % ========================================================================= % DEFINE THE ULTRASOUND TRANSDUCER % ========================================================================= % physical properties of the transducer transducer.number_elements = 96; % total number of transducer elements transducer.element_width = 10; % width of each element [grid points] transducer.element_length = 20; % 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] % 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 = 1540; % sound speed [m/s] transducer.focus_distance = 55e-3; %55e-3; % focus distance [m] transducer.elevation_focus_distance = 19e-3; % focus distance in the elevation plane [m] transducer.elevation_focus_distance = 25e-3; % focus distance in the elevation plane [m] transducer.steering_angle = 0; % steering angle [degrees] % apodization transducer.transmit_apodization = 'Rectangular'; transducer.receive_apodization = 'Rectangular'; % define the transducer elements that are currently active 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; % ========================================================================= % DEFINE SENSOR MASK % ========================================================================= % define a sensor mask through the central plane sensor.mask = zeros(Nx, Ny, Nz); switch MASK_PLANE case 'xy' % define mask sensor.mask(:, :, Nz/2) = 1; % store y axis properties Nj = Ny; j_vec = kgrid.y_vec; j_label = 'y'; case 'xz' % define mask sensor.mask(:, Ny/2, :) = 1; % store z axis properties Nj = Nz; j_vec = kgrid.z_vec; j_label = 'z'; end % set the record mode such that only the rms and peak values are stored if USE_STATISTICS sensor.record = {'p_rms', 'p_max'}; end % ========================================================================= % RUN THE SIMULATION % ========================================================================= % set the input settings input_args = {'DisplayMask', transducer.all_elements_mask, ... 'PMLInside', false, 'PlotPML', false, 'PMLSize', [PML_X_SIZE, PML_Y_SIZE, PML_Z_SIZE], ... 'DataCast', DATA_CAST, 'DataRecast', true, 'PlotScale', [-1/2, 1/2] * source_strength}; % stream the data to disk in blocks of 100 if storing the complete time % history if ~USE_STATISTICS input_args = [input_args {'StreamToDisk', 100}]; end tic % run the simulation sensor_data = kspaceFirstOrder3D(kgrid, medium, transducer, sensor, input_args{:}); toc % ========================================================================= % COMPUTE THE BEAM PATTERN USING SIMULATION STATISTICS % ========================================================================= if USE_STATISTICS % reshape the returned rms and max fields to their original position sensor_data.p_rms = reshape(sensor_data.p_rms, [Nx, Nj]); sensor_data.p_max = reshape(sensor_data.p_max, [Nx, Nj]); % plot the beam pattern using the pressure maximum figure; imagesc(j_vec * 1e3, (kgrid.x_vec - min(kgrid.x_vec(:))) * 1e3, sensor_data.p_max * 1e-6); xlabel([j_label '-position [mm]']); ylabel('x-position [mm]'); title('Total Beam Pattern Using Maximum Of Recorded Pressure'); colormap(jet(256)); c = colorbar; ylabel(c, 'Pressure [MPa]'); axis image; % plot the beam pattern using the pressure rms figure; imagesc(j_vec * 1e3, (kgrid.x_vec - min(kgrid.x_vec(:))) * 1e3, sensor_data.p_rms * 1e-6); xlabel([j_label '-position [mm]']); ylabel('x-position [mm]'); title('Total Beam Pattern Using RMS Of Recorded Pressure'); colormap(jet(256)); c = colorbar; ylabel(c, 'Pressure [MPa]'); axis image; % end the example return end