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1. Pmartc36
   

   Member
   Joined: Jun '21
   Posts: 3

   Hello there,

   I've ran function hounsfield2density on a nifti file but this error keeps coming up. Here is the error log.

   >> whos nifti_file
   Name Size Bytes Class Attributes

   nifti_file 260x311x260 42047200 int16

   >> nifti_test01
   Error using zeros
   Input following 'like' is not a numeric or logical array.

   Error in hounsfield2density (line 59)
   density = zeros(size(ct_data), 'like', ct_data);

   Error in nifti_test01 (line 3)
   [density, sound_speed] = hounsfield2density('nifti_file');

   This is the code I used.

   nifti_file = niftiread('att_map.nii');
   niftiinfo('t1w_pct.nii');

   %% Create the computational grid

   Nx = 400;
   Ny = 400;
   Nz = 400;
   dx = 50e-6;
   dy = 50e-6;
   dz = 50e-6;

   kgrid = makeGrid(Nx, dx, Ny, dy, Nz, dz);

   %% Define medium properties (using hounsfield2density

   density = hounsfield2density(nifti_file);

   Any suggestion as to what I should do?

   Posted 3 years ago #

2. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   The error message suggests you put the variable name in quotes:

   Error in nifti_test01 (line 3)
   [density, sound_speed] = hounsfield2density('nifti_file');

   What happens if you remove them?

   Posted 3 years ago #

3. Pmartc36
   

   Member
   Joined: Jun '21
   Posts: 3

   An error still pops up:

   WARNING: makeGrid will be deprecated in a future version of k-Wave.
   Update codes to use the syntax kgrid = kWaveGrid(...).

   Error using polyval (line 67)
   Inputs must be floats, namely single or double.

   Error in hounsfield2density (line 63)
   density(ct_data < 930) = polyval([1.025793065681423, -5.680404011488714], ct_data(ct_data < 930));

   Error in nifti_test01 (line 20)
   density = hounsfield2density(nifti_file);

   >>

   Posted 3 years ago #

4. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   You can often figure out what to do by looking at the error messages. This time it says

   Inputs must be floats, namely single or double

   This means it doesn't like that your image values are integers. You could try something like:

   density = hounsfield2density(single(nifti_file));

   Posted 3 years ago #

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