k-Wave

1. cdebossu
   

   Member
   Joined: Jul '17
   Posts: 1

   Hello,

   I am new to K-Wave, and have been trying to model an ultrasound pulse propagating through skull and brain matter. The transducer is held directly up to the head, which is covered in a thin layer of jelly (roughly the index of water). For the time being, I am placing the source (disc object) next to the receiver (disc object in same plane as the source). The source and receiver are far enough away from the boundaries of the computational grid, which is has a depth of X = 256 grid points.

   I have tried several different ways of removing reflections off of the boundaries of the computational grid (I played around with PlotPML = true and = false, I tried implementing kgrid.t_array), and I still can't seem to extinguish it.
   I would like to know how to eliminate the "ghost" reflection from the computational grid.

   Thank you.

   Posted 7 years ago #

2. yannick lecours
   

   Member
   Joined: Sep '17
   Posts: 1

   Hi cdebossu,

   Here is how it worked for me :

   I defined the PML size as : L_PML = 40, which basically means a 40-grid-points thick box around the useable volume/area (you can try different L_PML sizes, but 40 works for me). So your useable depth X is now equal to : Nx = 256-40 = 216.

   Then, in input_args, I have : input_args = {..., 'PMLInside', false, 'PMLSize', L_PML, 'PlotPML', false, 'PMLAlpha', 2, ...}

   Try these settings, and give me some feedback!

   Regards,
   Yan

   PS : I will eventually have to prog a skull and a brain too. If you don't mind, I would like to see how you built the masks and specs! Thanks :)

   Posted 7 years ago #

3. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Hi cdebossu,

   If your source and receivers our outside the PML, then I would guess what you're seeing is not related to the PML. (Note, turning plotting off doesn't change your simulation in any way.) Is it just that you are detecting the edge waves as they travel through the transducer? Do you see the same thing if you run your simulation in a completely homogeneous medium?

   Brad.

   Posted 7 years ago #

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