k-Wave

1. huanglin
   

   Member
   Joined: May '12
   Posts: 5

   Hi Dr.Brad Treeby,

   I am a fresh man for ultrasound imaging. Now I want to compute the pressure field distribution of a single element focused transducer in 2D or 3D, and I have tried both Ultrasound Beam Patterns Examples (I chosed transducer.number_elements = 1, I also modified the transducer.element_length with our transducer length and set transducer.radius = R, I do not know if this example is correct for a curved single element transducer simulation? ) and Transducer Field Patterns Example (I just know the focal length of our transducer, and I used R=2*f for calculation R. Therotically, a spherical curved transducer has focusing capability, I think this example is more suitable for my purpose) for simulation. Furthermore, is there any examples for focused transducer temperature distribution simulation?
   Please let me know which example is correct for my computation?

   Thanks,
   Lin

   Posted 10 years ago #

2. huanglin
   

   Member
   Joined: May '12
   Posts: 5

   Sorry, I just made a mistake, when I set transducer.radius = limited number in Ultrasound Beam Patterns Example, it reminded me that Only a value of transducer.radius = inf is currently supported.

   Posted 10 years ago #

3. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Hi Lin,

   For a single element transducer, I would define the source explicitly rather than using makeTransducer. For a focused transducer, there are two possibilities. First, you could create a curved transducer with the correct radius so that the ultrasound waves are geometrically focused (for example, using makeSphericalSection). Second, you could create a flat transducer and set the correct focus position using time delays. For example:

   % define a circular source element
   source_radius = 15;  % [grid points]
   source_shape  = makeDisc(Nx, Ny, Nx/2, Ny/2, source_radius);
   
   % assign source element to source mask
   source_z_pos = 12;  % [grid points]
   source.p_mask = zeros(Nx, Ny, Nz);
   source.p_mask(:, :, source_z_pos) = source_shape;
   
   % define source input
   source_freq = 2e6;  % [Hz]
   num_cycles = 5;
   source_signal = toneBurst(1/kgrid.dt, source_freq, num_cycles);
   
   % create time delays to focus the transducer and assign to source
   focus_position = [0, 0, 0]; % [m]
   source.p = focus(kgrid, source_signal, source.p_mask, focus_position, c0);

   Brad.

   Posted 10 years ago #

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