http://www.k-wave.org/forum/topic/plane-wave-scatters Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 13:32:24 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/plane-wave-scatters#post-5848 Mon, 13 Mar 2017 11:57:30 +0000 Bradley Treeby 5848@http://www.k-wave.org/forum/ <p>Hi Johan,</p> <p>You need to define a value for the density, although you don't necessarily need to make it heterogeneous. However, at least in soft tissue, there is a reasonably strong correlation between sound speed and density (see <a href="http://asa.scitation.org/doi/abs/10.1121/1.1336896">here</a> for example). </p> <p>I'd also advise constraining the sound speed and density between biologically relevant minimum and maximum values. Otherwise, <code>randn</code> may select a very large or small value (which is what you have noticed).</p> <p>Hope that helps,</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/plane-wave-scatters#post-5834 Fri, 17 Feb 2017 13:59:22 +0000 johanbn 5834@http://www.k-wave.org/forum/ <p>Hi, I'm a student from Norway. </p> <p>In my master thesis need I to have data from scattering of plane wave, with a given steering angle. And with assumption that the medium has different sound speed maps in given regions. </p> <p>I tried to modify B-mode transducer example by setting focus and elevation focus to inf.<br /> And some modification on how to set up the medium. </p> <p>My goal is too have data that is just a speckle pattern where you cant dissolve any region even if some regions have different SOS. </p> <p>And to get the code to run, I had to define a density_map. Is this correct to include? Given that I want to characterize my region whit different SOS ?</p> <p>Is this possible to generate?</p> <p>My changes to the code:</p> <p>% properties used to derive the beamforming delays<br /> transducer.focus_distance = inf;<br /> transducer.elevation_focus_distance = inf;<br /> transducer.sound_speed = c0; % sound speed [m/s]<br /> transducer.steering_angle = 0; % steering angle [degrees]</p> <p>% define a random distribution of scatterers for the medium<br /> background_map = 75*randn([Nx_tot, Ny_tot, Nz_tot]);</p> <p>% define a sligthly translated data for region whit different SOS.<br /> scattering_c0 = c0 + 25 + background_map;<br /> scattering_rho0 = scattering_c0/1.5;</p> <p>% define properties<br /> sound_speed_map = c0*ones(Nx_tot, Ny_tot, Nz_tot).*background_map;<br /> density_map = rho0*ones(Nx_tot, Ny_tot, Nz_tot).*background_map;</p> <p>% define a sphere for a scattering region whit different SOS.<br /> radius = 4.5e-3; % [m]<br /> x_pos = 20e-3; % [m]<br /> y_pos = 20e-3; % [m]<br /> scattering_region1 = makeBall(Nx_tot, Ny_tot, Nz_tot, round(x_pos/dx), round(y_pos/dx), Nz_tot/2, round(radius/dx));</p> <p>% assign region<br /> sound_speed_map(scattering_region1 == 1) = scattering_c0(scattering_region1 == 1);<br /> density_map(scattering_region1 == 1) = scattering_rho0(scattering_region1 == 1);</p> <p>I also had to set </p> <p>medium.sound_speed_ref = 1540;</p> <p>otherwise It was like 639876. </p> <p>Thank you<br /> Johan </p>