k-Wave

1. Suryakant
   

   Member
   Joined: Jul '15
   Posts: 6

   We tried running the aforementioned example however we were getting a few errors
   The first error being that it says "error using *" in the following
   input_signal = (source_strength./(medium.sound_speed*medium.density)).*inputsignal

   Can anyone please help us on how to correct this error

   % defining an ultrasound sognle frequency toneburst
   sample_frequency =20000000;

   signal_frequency =1000000;
   num_cycles = 10;

   Nx =128;
   Ny =128;
   Nz =128;
   dx = .00001;
   dy = .00001;
   dz = .00001;
   kgrid = makeGrid(Nx,dx,Ny,dy,Nz,dz);
   kgrid.t_array = makeTime(kgrid,1500);
   medium.sound_speed =1500*ones(Nx,Ny,Nz);
   medium.sound_speed(1:Nx/2,:,:)=1800;
   medium.density =1000*ones(Nx,Ny,Nz);

   medium.density(:,Ny/4:end, :)=1200;
   signal = toneBurst(sample_frequency,signal_frequency,num_cycles);
   toneBurst(sample_frequency,signal_frequency,num_cycles,'Plot',true);
   source_strength = 1*10^6;
   tone_burst_freq = .5*10^6;
   tone_burst_cycles = 5;
   input_signal = toneBurst(1/kgrid.dt,tone_burst_freq,tone_burst_cycles);
   imput_signal = (source_strength./(medium.sound_speed*medium.density)).*input_signal;
   transducer.number_elements = 64;
   transducer.element_width =1 ;
   transducer.element_length = 12;
   transducer.element_spacing = 0;
   transducer.radius = inf;

   transducer_width = transducer.number_elements*transducer.element_width + (transducer.number_elements -1)*transducer.element_spacing;
   transducer.position = round([1,32-transducer_width/2,32-transducer.element_length/2]);
   transducer.sound_speed = 1540;
   transducer.focus_distance = 20*10^-3;
   transducer.elevation_focus_distance = 19*10^-3;
   transducer.steering_angle = 0;
   transducer.transmit_apodization = 'Rectangular';
   transducer.receive_apodization = 'Rectangular';
   transducer.active_elements = zeros(transducer.number_elements,1);
   transducer.active_elements(21:52) = 1;
   transducer.input_signal = input_signal;
   transducer = makeTransducer(kgrid,transducer);
   [sensor_data] = kspaceFirstOrder3D(kgrid,medium,transducer, sensor,input_args{:});

   Posted 8 years ago #

2. Anthony
   

   Member
   Joined: Apr '13
   Posts: 96

   Hi Suryakant,

   It is a problem of matrix size when you write :
   

   imput_signal = (source_strength./(medium.sound_speed*medium.density)).*input_signal;

   First of all, you should use .* instead of * to multiply term by therm the density and the sound speed... but I don't exactly get what you are trying to do (I am not familiar with the use of the transducer class): if the input signal is the same at every point of your transducer, should'nt you set your source term as a matrix of size [1,Nt] (or [Nt,1], I don't remember), with Nt the number of time steps?
   If the signal is different at every point of your transducer (phased array for example), I guess your source term should be of size [Ntr,Nt] (or [Nt, Ntr], I don't remember), with Ntr the number of points in your transducer.

   Your definition of the transducer does not seem correct. Once again I am not familiar with the transducer class as I do everything manually but look at the help of the function makeTransducer to define its properties. I am not sure you are allowed to manually set transducer.number_elements and the other properties directly.

   You can probably find the other examples helpful too.

   Good luck :-)
   Anthony

   PS: by the way, you have a little typo in your code : "imput_signal" instead of "input_signal".

   Posted 8 years ago #

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