http://www.k-wave.org/forum/topic/heterogeneous-attenuation-values Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 02:57:30 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/heterogeneous-attenuation-values#post-7318 Thu, 26 Mar 2020 11:24:40 +0000 Bradley Treeby 7318@http://www.k-wave.org/forum/ <p>Hi ninasnum,</p> <p>Yes, in this example the value for <code>tgc_alpha_db_cm</code> needs to be a scalar. If you want to account for frequency dependent absorption, then you could look at the <code>attenComp</code> function.</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/heterogeneous-attenuation-values#post-7317 Tue, 24 Mar 2020 22:28:11 +0000 ninasnum 7317@http://www.k-wave.org/forum/ <p>Hi, I'm also trying to write ultrasound simulation with heterogenous attentuation. At the moment, it is having a ball of muscle inside water medium</p> <p>From the ultrasound example, the time gain compensation step seems to work only with medium.alpha_coeff as a number, not varying at the bsxfun function (matlab complains to me about dimensions when I made it heterogeneous).<br /> <pre><code>% ----------------------------- % Time Gain Compensation % ----------------------------- % create radius variable assuming that t0 corresponds to the middle of the % input signal t0 = length(input_signal) * kgrid.dt / 2; r = c0 * ( (1:length(kgrid.t_array)) * kgrid.dt - t0 ) / 2; % [m] % define absorption value and convert to correct units tgc_alpha_db_cm = medium.alpha_coeff * (tone_burst_freq * 1e-6)^medium.alpha_power; tgc_alpha_np_m = tgc_alpha_db_cm / 8.686 * 100; % create time gain compensation function based on attenuation value and % round trip distance tgc = exp(tgc_alpha_np_m * 2 * r); % apply the time gain compensation to each of the scan lines scan_lines = bsxfun(@times, tgc, scan_lines);</code></pre> <p>If I have medium.alpha_coeff spatially varying (such as coeff for muscle where ball is and rest have coeff of water), does that mean I have to change the tgc_alpha_db_cm calculation to just use the default coeff of water so that the bsxfun function will work? </p> http://www.k-wave.org/forum/topic/heterogeneous-attenuation-values#post-7094 Fri, 18 Oct 2019 20:26:17 +0000 Bradley Treeby 7094@http://www.k-wave.org/forum/ <p>Hi drewc830,</p> <p>It's possible to have a spatially varying <code>medium.alpha_coeff</code> but not <code>medium.alpha_power</code>. Just assign the values the same as the sound speed.</p> <p>If you're trying to simulate highly absorbing materials such as bone, you could make use of <a href="http://www.k-wave.org/downloads/fitPowerLawParamsMulti.m">this function</a>.</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/heterogeneous-attenuation-values#post-7076 Wed, 16 Oct 2019 19:58:59 +0000 drewc830 7076@http://www.k-wave.org/forum/ <p>I am writing a simulation to show the effectiveness (or lack thereof) of b-mode ultrasound through bone/tissue interfaces. I have some results thus far that are decent but could be improved upon by adjusting some parameters in the code.</p> <p>I was wondering if it was possible to assign an attenuation coefficient map instead of using the constant value provided in the 3d_bmode example. </p> <p>I couldn't find any other topics on this specific item. I can also post my results if that is helpful. </p>