k-Wave

1. lirj
   

   Member
   Joined: Jan '15
   Posts: 9

   Hi Dr. Treeby and Dr. Cox,
   My question is about the absorption coefficient setting of different mediums in a ultrasound simulation.
   We want to design a medium with different absorption coefficient in each position, in order to implement the simulation of real human body tissue. But we can only find the single setting of absorption coefficient from the K-WAVE toolbox. The related setting of the absorption coefficients are as follow:
   (1)medium.BonA, (2)medium.alpha_power, (3)medium.alpha_coeff.
   They all can only be set up for a scalar, but as we need, we need to set up the absorption coefficient of the medium like medium.sound_speed and medium.density.
   Thus, we want to know which variable can be set up to realize the function.
   We hope you can help us to solve this problem. Thank you!
   Best wishes!
   Lirj
   2016.6.22

   Posted 7 years ago #

2. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,640

   Hi Lirj,

   Both medium.alpha_coeff and medium.BonA can be defined as matrices in the same way as the sound speed and density. In the current version of k-Wave, medium.alpha_power must be a scalar because of the way acoustic absorption is encoded using a fractional Laplacian.

   If this is a problem, one option is to select a suitable scalar value for medium.alpha_power, and then perturb the values of medium.alpha_coeff so that you get the correct absorption in dB/cm at a particular reference frequency, i.e.,

   alpha_coeff_new = alpha_coeff * f_MHz ^ (y - y_ref);

   Here alpha_coeff and y are the actual power law values (e.g., from book values or measurements), y_ref is the reference value for medium.alpha_power, and alpha_coeff_new is the modified value to pass to k-Wave.

   Brad.

   Posted 7 years ago #

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