k-Wave

1. milksoup
   

   Member
   Joined: May '19
   Posts: 10

   Hello all,

   I've been referring to the k-wave manual to try and understand the source structure for the purpose of modelling a focused ultrasound source going through a skull medium.

   The three types of sources listen are
   1. initial pressure distribution
   2. time-varying pressure source (corresponds to mass)
   3. time-varying particle velocity source (corresponds to force)

   My background in physics and applied math isn't the most thorough, so excuse the following inquiry if its overlooking something rudimentary.

   I'm not grasping the differences between the 2nd (I'll call it mass) and 3rd (I'll call it force) types listed well enough to know which is more suitable for simulating a focused ultrasound beam.

   Does it even matter? From reading the manual it looks to me that the force type may be better for 3D simulations, although I'm not at all sure.

   I consulted the equations but that left me with more questions than answers.

   Any help clearing this up would be appreciated.

   Thanks.

   Posted 4 years ago #

2. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Hi milksop,

   The mass and force sources will give you different fields. Acoustically, one acts as a monopole and one as a dipole. If you look at the first two examples under the Time Varying Source Problems (you can run these from the MATLAB help browser), this should hopefully help to clarify things.

   For modelling a focused beam from an idealised transducer, I would typically use a uniform additive pressure source in k-Wave (note, the uniform injection of pressure in free-space does not imply the actual surface pressure is uniform).

   Brad.

   Posted 4 years ago #

3. milksoup
   

   Member
   Joined: May '19
   Posts: 10

   Thanks for clearing this up!

   What I'm understanding is that the "additive pressure source" you would use for a focused beam would be utilising the 2nd source with a default "additive" source.p_mode, which is used in the monopole example.

   I don't know what you mean by "uniform", though. Can you please explain?

   I looked at the examples and found one that seems to follow nicely from the monopole example to suit my purposes, the Simulating Transducer Field Patterns Example. I'll see if that's what I need.

   Posted 4 years ago #

4. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Yes, that's right. Uniform just meaning that the input signal is the same everywhere over the transducer surface. There are some additional examples in the examples folder of the new k-Wave array class that might also be useful.

   Posted 3 years ago #

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