http://www.k-wave.org/forum/topic/absorption-model Support for the k-Wave MATLAB toolbox en-US Tue, 12 May 2026 23:28:19 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/absorption-model#post-7072 Tue, 08 Oct 2019 20:43:55 +0000 vich 7072@http://www.k-wave.org/forum/ <p>There's only so much you can do with limited information. If you know the attenuation (in dB/cm) the authors reported and the frequency (in MHz) of the ultrasound in their experiments, you could simply divide the attenuation by the frequency squared. There is no way to know if your power law exponent of 2 is correct, though.</p> <p>If the authors provided multiple attenuation values at different frequencies, you can fit a power regression model to the data points. This essentially means fitting the parameters a, b in:</p> <p><code><br /> log(attenuation) = a + b * log(frequency)<br /> </code></p> <p>via ordinary least squares. Once the parameters have been estimated, you can take an exponential to get:</p> <p><code><br /> exp(log(attenuation)) = exp(a + b * log(frequency))<br /> attenuation = exp(a) * exp(log(frequency)) ^ b<br /> attenuation = exp(a) * frequency ^ b<br /> </code></p> <p>When using k-Wave, <code>exp(a)</code> becomes <code>medium.alpha_coeff</code> and <code>b</code> becomes <code>medium.alpha_power</code>.</p> <p>Perhaps other people here might have different suggestions? </p> http://www.k-wave.org/forum/topic/absorption-model#post-7057 Mon, 23 Sep 2019 00:55:17 +0000 elliotP 7057@http://www.k-wave.org/forum/ <p>Hello everyone,</p> <p>Unit of the absorption coefficient for compressional waves and shear waves is dB/(MHz^2 cm) in a pstdElastic2D simulation (power-law exponent is set to y = 2).<br /> When I look for papers which are related to a transcranial application, authors use dB/cm unit such as 13.3 dB/cm (paper name: Attenuation, scattering, and absorption of ultrasound in the skull bone.)<br /> How can I convert dB/cm to dB/(MHz^2 cm)?</p> <p>Thank you,<br /> Michael </p>