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k-Wave User Forum » User Favorites: zhaoxiang zhaoxiang Support for the k-Wave MATLAB toolbox en-US Tue, 12 May 2026 23:06:04 +0000 http://bbpress.org/?v=1.0.2 <![CDATA[Search]]> q http://www.k-wave.org/forum/search.php HD Y on "Using source.p to specify pressure distribution" http://www.k-wave.org/forum/topic/using-sourcep-to-specify-pressure-distribution#post-9188 Wed, 19 Feb 2025 23:21:34 +0000 HD Y 9188@http://www.k-wave.org/forum/ Hi, it seems I found some discussions on the implementation of Dirichlet boundary conditions in this post. But I still did not get how the scaling factor is set in general. On the other hand, I saw some good results in Figure 2 of the following publication: Modelling Nonlinear Ultrasound Propagation in Absorbing Media using the k-Wave Toolbox: Experimental Validation. May I ask in this reference, what exact scaling factor is used in order to get such good agreement between simulation results and experimental results. Thanks nhaidour on "Alpha version of kWaveArray (off-grid sources)" http://www.k-wave.org/forum/topic/alpha-version-of-kwavearray-off-grid-sources/page/2#post-8873 Fri, 28 Jul 2023 10:50:03 +0000 nhaidour 8873@http://www.k-wave.org/forum/ Hi Bradley, I'm simulating a disc element using karray.addDiscElement, but when I draw the 3D plot of this element, it seems the shape of the element is not a disc, it looks like it's rectangle, is this normal? Cordially, Jinhyuk Kim on "Alpha version of kWaveArray (off-grid sources)" http://www.k-wave.org/forum/topic/alpha-version-of-kwavearray-off-grid-sources/page/2#post-8778 Tue, 30 May 2023 02:15:16 +0000 Jinhyuk Kim 8778@http://www.k-wave.org/forum/ Thanks, Bradley! I have to adjust the position of the ultrasound transducer, right? I'll try and research successfully! Bradley Treeby on "Alpha version of kWaveArray (off-grid sources)" http://www.k-wave.org/forum/topic/alpha-version-of-kwavearray-off-grid-sources/page/2#post-8761 Thu, 18 May 2023 06:25:54 +0000 Bradley Treeby 8761@http://www.k-wave.org/forum/ Hi Jinhyuk Kim, In <code>kWaveArray</code>, the element positions must be set in physical space (not grid space). So, in your example, there are no elements within the grid, so the mask ends up being zero (hence the error message). Brad Jinhyuk Kim on "Alpha version of kWaveArray (off-grid sources)" http://www.k-wave.org/forum/topic/alpha-version-of-kwavearray-off-grid-sources/page/2#post-8746 Thu, 27 Apr 2023 10:02:31 +0000 Jinhyuk Kim 8746@http://www.k-wave.org/forum/ Hi everyone, I have a problem with the kspaceFirstOrder2D. error message is 'source.p_mask must be a binary grid with at least one element set to 1. I want to find acoustic fiend arising from array used kwavearray class, however, I found above error messasge. Here is my code. karray = kWaveArray; % define the grid parameters pml_size = 20; Nx = 552 - 2 * pml_size; % [grid points] Ny = 552 - 2 * pml_size; % [grid points] dx = 1e-3; % [m] dy = 1e-3; % [m] % create the computational grid kgrid = kWaveGrid(Nx, dx, Ny, dy); %% ALPHA COEFF medium.alpha_coeff = 0.02 * ones(Nx, Ny); % [dB/(MHz^y cm)] WATER medium.alpha_power = 1.5; %% SPEED medium.sound_speed = 1500 * ones(Nx, Ny); % WATER default fill! [m/s] % %skull %% DENSITY medium.density = 1000 * ones(Nx, Ny); % WATER default fill [kg/m^3] freq = 200*10^3; % [Hz] amp = 0.3e6; % 0.53[MPa] radius = 10e-3; % [m] diameter = 15e-3; % [m] focus_pos = [Nx/2, Ny/2]; % [m] % add arc shaped element elem_pos = [Nx/10, Ny/2]; % [m] karray.addArcElement(elem_pos, radius, diameter, focus_pos); % add arc shaped element elem_pos = [Nx/10, Ny/2.5]; % [m] karray.addArcElement(elem_pos, radius, diameter, focus_pos); % add arc shaped element elem_pos = [Nx/10, Ny/3.0]; % [m] karray.addArcElement(elem_pos, radius, diameter, focus_pos); source.p_mask = karray.getArrayBinaryMask(kgrid); display_mask = source.p_mask; % calculate the time step using an integer number of points per period ppw = 100; % points per wavelength cfl = 0.1; % cfl number ppp = 41; % points per period T = 1 / freq; % period [s] dt = 4e-8; % time step [s] % calculate the number of time steps to reach steady state t_end = 40.0575e-5; Nt = round(t_end / dt); % create the time array kgrid.setTime(Nt, dt); % define the input signal source.p = createCWSignals(kgrid.t_array, freq, [amp, amp, amp], 0); sensor.mask = ones(Nx, Ny); sensor.record = {'p', 'p_max_all'}; % record the last 3 cycles in steady state num_periods = 15; T_points = round(num_periods * T ./ kgrid.dt); sensor.record_start_index = Nt - T_points + 1; % set the input arguements input_args = {'PMLInside', false,'PlotLayout', true, 'PlotPML', false, 'DisplayMask', display_mask, 'PlotScale', [-1, 1] * amp}; % run the acoustic simulation sensor_data = kspaceFirstOrder2D(kgrid, medium, source, sensor, input_args{:}); Thanks zengqw2021 on "Alpha version of kWaveArray (off-grid sources)" http://www.k-wave.org/forum/topic/alpha-version-of-kwavearray-off-grid-sources/page/2#post-8745 Fri, 21 Apr 2023 06:03:48 +0000 zengqw2021 8745@http://www.k-wave.org/forum/ Hi everyone, Is there a way for me to get grid points form part of the specified element. As for example_at_array_as_sensor.m, I got a sensor_data array of size 6748 by 1207. There is 20 elements. But, how could I tell which transducer these 6748 time series belong to. I find a property named 'getElementBinaryMask' may be work. But when I run it in the following way, I get an error 'Method, attribute, or field 'getElementBinaryMask' of class 'kWaveArray' not recognized.'. mask2 = karray.getElementBinaryMask(kgrid, 1); % grid points form part of the specified element Does anyone know how to solve this problem？ Bradley Treeby on "Alpha version of kWaveArray (off-grid sources)" http://www.k-wave.org/forum/topic/alpha-version-of-kwavearray-off-grid-sources/page/2#post-8673 Mon, 28 Nov 2022 15:56:34 +0000 Bradley Treeby 8673@http://www.k-wave.org/forum/ Hi HN, Yes at the moment you need to define them manually. The <a href="http://www.k-wave.org/documentation/example_at_linear_array_transducer.php">Modelling A Linear Array Transducer Example</a> shows one way to do this. Brad. nhaidour on "Alpha version of kWaveArray (off-grid sources)" http://www.k-wave.org/forum/topic/alpha-version-of-kwavearray-off-grid-sources/page/2#post-8672 Mon, 28 Nov 2022 13:37:46 +0000 nhaidour 8672@http://www.k-wave.org/forum/ Thank you for your response ! I want to modelise a 2D Probe that contain elements and an inter-space element in 3D, and I think the best way is to use KwaveArray class! But I did not find the function that would allow me to declare the number of elements with an inter-space and their position. Or do I have to declare each element manually? Best Regards, HN Bradley Treeby on "Alpha version of kWaveArray (off-grid sources)" http://www.k-wave.org/forum/topic/alpha-version-of-kwavearray-off-grid-sources/page/2#post-8670 Tue, 22 Nov 2022 21:11:11 +0000 Bradley Treeby 8670@http://www.k-wave.org/forum/ Yes - there are several examples in the included documentation under “modelling transducer arrays”. nhaidour on "Alpha version of kWaveArray (off-grid sources)" http://www.k-wave.org/forum/topic/alpha-version-of-kwavearray-off-grid-sources/page/2#post-8669 Tue, 22 Nov 2022 16:12:49 +0000 nhaidour 8669@http://www.k-wave.org/forum/ Hello, Is there some examples for using the KwaveArray ? Best Regards, HN Bradley Treeby on "Alpha version of kWaveArray (off-grid sources)" http://www.k-wave.org/forum/topic/alpha-version-of-kwavearray-off-grid-sources#post-8642 Tue, 08 Nov 2022 10:13:50 +0000 Bradley Treeby 8642@http://www.k-wave.org/forum/ Noting that <code>kWaveArray</code> is now part of k-Wave v1.4. bencox on "Doubts converting pressure into heat deposition" http://www.k-wave.org/forum/topic/doubts-converting-pressure-into-heat-deposition#post-8579 Wed, 13 Jul 2022 18:56:12 +0000 bencox 8579@http://www.k-wave.org/forum/ Hi ganrielcathoud, That expression comes from 2*alpha*I_av where I is the time-averaged intensity. In a plane wave, which is a good approximation in many practical cases, such as at the focus of a transducer, I_av is related to the acoustic pressure by 0.5*p_max^2/(density*sound speed), where p_max incorporates the effect of the absorption on the wave amplitude. Going back a step, 2*alpha*I_av is the gradient of the average intensity: if the average intensity in a plane wave is decreasing, there must be energy being left behind. That is the energy that is being converted to heat. Look up some reviews on ultrasound therapy for more details on this. Best wishes Ben bencox on "Alpha version of kWaveArray (off-grid sources)" http://www.k-wave.org/forum/topic/alpha-version-of-kwavearray-off-grid-sources#post-8573 Wed, 13 Jul 2022 17:31:30 +0000 bencox 8573@http://www.k-wave.org/forum/ Hi quetaijiangchu and LewisR, There is not such an example yet, no, although the idea behind kWaveArray does have the capability of modelling just such sources. Essentially, given a desired surface, it is necessary to convolve it with the bandlimited interpolant, which has the form <code>sinc(x * pi / dx)</code>, and then sample the resulting function at the grid points to give the weights used in kWaveArray. The details are given in <a href="http://bug.medphys.ucl.ac.uk/papers/2019-Wise-JASA.pdf">this paper</a>. We will add more functionality in due course when we integrate it into k-Wave properly. Best wishes Ben gabrielcathoud on "Doubts converting pressure into heat deposition" http://www.k-wave.org/forum/topic/doubts-converting-pressure-into-heat-deposition#post-8565 Wed, 13 Jul 2022 14:51:26 +0000 gabrielcathoud 8565@http://www.k-wave.org/forum/ I'm simulating the heating generated by the use of ultrasound in the brain. The ultrasound simulation is working fine, but I am having difficulties with the temperature simulation. How do I convert pressure aplied into deposited heat? I found a conversion here on the forum, but I don't understand why: source.Q = alpha_np.*sensor_data.p_max_all.^2./(medium.density .* medium.sound_speed); I appreciate any help. The whole temperatura simulation is: clear source; medium.thermal_conductivity = thermal_conductivity_water*ones(Nx,Ny); medium.thermal_conductivity(head_mask==1) = thermal_conductivity_bone; medium.specific_heat = specific_heat_water*ones(Nx,Ny); medium.specific_heat(head_mask==1) = specific_heat_bone; alpha_np = db2neper(medium.alpha_coeff, medium.alpha_power)... *(2 * pi * source_freq).^medium.alpha_power; dt = 0.001; source.Q = alpha_np.*sensor_data.p_max_all.^2./(medium.density .* medium.sound_speed); source.T0 = 37; input_args = {'PlotSim', true}; kdiff = kWaveDiffusion(kgrid, medium, source, [], input_args{:}); on_time = duration_of_stimulus; % [s] off_time = 60; % [s] kdiff.takeTimeStep(round(on_time / dt), dt); T1 = kdiff.T; kdiff.Q = 0; dt = 0.1; kdiff.takeTimeStep(round(off_time / dt), dt); T2 = kdiff.T; quetaijiangchu on "Alpha version of kWaveArray (off-grid sources)" http://www.k-wave.org/forum/topic/alpha-version-of-kwavearray-off-grid-sources#post-8552 Wed, 15 Jun 2022 08:28:47 +0000 quetaijiangchu 8552@http://www.k-wave.org/forum/ Is there an example of how to create 3D irregularities using function addCustomElement? LewisR on "Alpha version of kWaveArray (off-grid sources)" http://www.k-wave.org/forum/topic/alpha-version-of-kwavearray-off-grid-sources#post-8524 Wed, 04 May 2022 14:19:03 +0000 LewisR 8524@http://www.k-wave.org/forum/ Hi Brad, Can kWaveArray support rectangular curved elements? Specifically curvature to both the height and width of the element. Or would this need to be done using the custom element option? I'm a little confused with how to use the addCustomElement method, would it be possible for you to do an example? If in fact it can be used to solve my problem. Thanks in advance, Lewis Deepak Sonker on "Differences in focus pressure between k-Wave and analytical transducer model" http://www.k-wave.org/forum/topic/differences-in-focus-pressure-between-k-wave-and-analytical-transducer-model#post-8283 Fri, 06 Aug 2021 21:03:18 +0000 Deepak Sonker 8283@http://www.k-wave.org/forum/ Thank you I have got the correct pressure with kWaveArray class. Bradley Treeby on "Differences in focus pressure between k-Wave and analytical transducer model" http://www.k-wave.org/forum/topic/differences-in-focus-pressure-between-k-wave-and-analytical-transducer-model#post-8254 Wed, 21 Jul 2021 16:13:41 +0000 Bradley Treeby 8254@http://www.k-wave.org/forum/ Hi deepak11, There are some examples of doing this comparison in the new <a href="http://www.k-wave.org/forum/topic/alpha-version-of-kwavearray-off-grid-sources">kWaveArray</a> class that might show you where you're going wrong. Note, if you're using a grid-based source, you'll have to include an extra scaling factor (or weight the source amplitudes) as discuss in <a href="http://bug.medphys.ucl.ac.uk/papers/2016-Martin-IEEETUFFC.pdf">this paper</a>. Brad deepak11 on "Differences in focus pressure between k-Wave and analytical transducer model" http://www.k-wave.org/forum/topic/differences-in-focus-pressure-between-k-wave-and-analytical-transducer-model#post-8244 Tue, 20 Jul 2021 23:51:29 +0000 deepak11 8244@http://www.k-wave.org/forum/ Hi, First of all thank you for building this amazing toolbox. I have simulated the bowel transducer in 3D and then compared the focus pressure amplitude with the analytical model of a concave spherical transducer (from Theory of Focusing Radiators by H.T. O'Neil). I also checked this analytical model results from the Sonic Concepts transducer (H-276) and it was correct. I couldn't find the mistake in my code I think I have done everything correctly but the results shouldn't deviate that much (like the peak pressure at the focus must be 58 MHz but the simulated pressure is 46.8 MHz ). I have posted the code below: (`% define the grid parameters 3D Nx = 150; % [grid points] Ny = 150; % [grid points] Nz = 92; dx = 0.1e-3; % [m] dy = 0.1e-3; % [m] dz = 0.1e-3; % [m] % create the computational grid kgrid = kWaveGrid(Nx, dx, Ny, dy, Nz, dz); % define the properties of the propagation medium water medium.sound_speed = 1500; % [m/s] medium.density = 1000; % [kg/m^3] medium.alpha_coeff = 0.025; % [dB/(MHz^y cm)] medium.alpha_power = 1.5; % define parameters grid_size = [150,150,92]; bowl_pos = [Nx/2, Ny/2, 2]; diameter = 15e-3; % [m] radius = 8.5e-3; % [m] focus_pos = [Nx/2, Ny/2, 87]; freq = 1.5e6; % [Hz] amp = 2.06e6; % [Pa] % create bowl source.p_mask = makeBowl(grid_size, bowl_pos, round(radius / dx), round(diameter / dx)+1, focus_pos, 'Plot', true); % calculate the time step using an integer number of points per period ppw = max(medium.sound_speed(:)) / (freq * dx); % points per wavelength cfl = 0.3; % cfl number ppp = ceil(ppw / cfl); % points per period T = 1 / freq; % period [s] dt = T / ppp; % time step [s] % calculate the number of time steps to reach steady state t_end = sqrt( kgrid.x_size.^2 + kgrid.y_size.^2 + kgrid.z_size.^2 ) / max(medium.sound_speed(:)); Nt = round(t_end / dt); % create the time array kgrid.setTime(Nt, dt); % define the input signal source.p = createCWSignals(kgrid.t_array, freq, amp, 0); % set the sensor mask to cover the entire grid sensor.mask = ones(Nx, Ny, Nz); sensor.record = {'p','p_rms','u','u_rms', 'I','I_avg'}; % record the last 3 cycles in steady state num_periods = 3; T_points = round(num_periods * T / kgrid.dt); sensor.record_start_index = Nt - T_points + 1; % set the input arguements input_args = {'PMLInside', false, 'PlotPML', false, 'DisplayMask', ... 'off', 'PlotScale', [-1, 1] * amp}; % run the acoustic simulation sensor_data = kspaceFirstOrder3D(kgrid, medium, source, sensor, input_args{:}); % convert the absorption coefficient to nepers/m alpha_np = db2neper(medium.alpha_coeff, medium.alpha_power) * ... (2 * pi * freq).^medium.alpha_power; % extract the pressure amplitude at each position p = extractAmpPhase(sensor_data.p, 1/kgrid.dt, freq); % reshape the data, and calculate the volume rate of heat deposition p = reshape(p, Nx, Ny, Nz); Eric Miller on "Alpha version of kWaveArray (off-grid sources)" http://www.k-wave.org/forum/topic/alpha-version-of-kwavearray-off-grid-sources#post-8211 Fri, 11 Jun 2021 21:21:05 +0000 Eric Miller 8211@http://www.k-wave.org/forum/ Hi Brad, Works like a charm! Another question: I have an annular array with a rectangular central aperture. Trying to work though the kWaveArray class to see what I'll need to tweak. I have my ring inner and outer diameters, I only need to remove the parts of the rings that overlap with the rectangular aperture. Any guidance on doing this such that the grid weights come out correct? -Eric