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.
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.
I couldn't find any other topics on this specific item. I can also post my results if that is helpful.
Hi drewc830,
It's possible to have a spatially varying medium.alpha_coeff but not medium.alpha_power. Just assign the values the same as the sound speed.
If you're trying to simulate highly absorbing materials such as bone, you could make use of this function.
Brad.
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
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).
% -----------------------------
% 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);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?
Hi ninasnum,
Yes, in this example the value for tgc_alpha_db_cm needs to be a scalar. If you want to account for frequency dependent absorption, then you could look at the attenComp function.
Brad.
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