k-Wave

1. uhultrasound
   

   Member
   Joined: Jul '16
   Posts: 13

   Hi,

   Thank you very much for sharing the wonderful program. I am testing the Matlab example example_ewp_3D_simulation.m. Since I can't figure out what the sensors' positions are and how many sensors there are, I don't quite understand the final output graph of sensor position vs. time. I was wondering if you please help me with the following questions:

   1. What the sensors' positions are and how many sensors there are? I don't quite follow "define sensor mask in x-y plane using cuboid corners, where a rectangular mask is defined using the xyz coordinates of two opposing corners in the form [x1, y1, z1, x2, y2, z2]." Is it a rectangular sensor 2D-array? Then, how to index the 2D-array sensors?

   2. May I visualize the sensors by using voxelPlot function? I tried "voxelPlot(double(cart2grid(kgrid, sensor.mask)));", but it doesn't work.

   3. For ultrasound focusing, I was wondering if I could assume the ultrasound wave propagates in media as spherical waves without focusing? May I do this in example_ewp_3D_simulation.m?

   Many thanks and have a great day.

   John

   Posted 8 years ago #

2. uhultrasound
   

   Member
   Joined: Jul '16
   Posts: 13

   Hi,

   I tested the program further. It seems the sensor mask is a rectangular mask. So, it seems the final output graph is not a graph of sensor position vs. time, but it is a graph of the recorded maximum pressure map of X-axis vs. Y-axis (there is no time information), am I right? If so, I was wondering if you could please help let me know how to save data of the pressure vs. time for the sensor mask in example_ewp_3D_simulation.m?

   In addition, it seems when I removed the "source.ux = focus(kgrid, source.ux, source.u_mask, [0, 0, 0], 1500);" code, the ultrasound wave will propagate in media as spherical waves.

   Many thanks,

   John

   Posted 8 years ago #

3. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Hi John,

   To understand the different ways the sensor mask can be defined (and how it is indexed), I would suggest working through the first few examples under the "Initial Value Problems" heading in the k-Wave help (this can be accessed through the MATLAB help browser as described in the manual). To change what is recorded, you need to modify the value of sensor.record. For more details, see the "Recording The Particle Velocity Example" or the k-Wave manual.

   For this particular example, the source is a velocity source. Thus without focusing, each source element propagates as a point dipole (rather than a point monopole which would emit a spherical wave). See the first two examples under the "Time Varying Source Problems" heading for more details of the field shape. If you want to create a monopole source, you could instead define the normal components of the stress.

   Hope that helps,

   Brad.

   Posted 8 years ago #

4. uhultrasound
   

   Member
   Joined: Jul '16
   Posts: 13

   Hi Brad,

   Thank you very much and have a good weekend.

   John

   Posted 8 years ago #

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