fft2 in Matlab with a dicom images (MRI)

Question

I want to perform a 2 dimensional fourier transform on an image slice of a cranial MRI. I have tried the following codes and have not been successful: (error messages included below)

>> clear all
>> 
>> info = dicominfo('MR000026.dcm');
Y = dicomread(info);
J=imadjust(Y,stretchlim(Y),[0 1]);
F = fftshift(fft2(fftshift(J)));
Undefined function 'fftn' for input arguments of type 'int16'.

Error in fft2 (line 19)
        f = fftn(x);

>> info = dicominfo('MR000026.dcm');
Y = dicomread(info);
F = fftshift(fft2(fftshift(Y)));
Undefined function 'fftn' for input arguments of type 'int16'.

Error in fft2 (line 19)
        f = fftn(x);

>> info = dicominfo('MR000026.dcm');
Y = dicomread(info);
F = fft2(Y);
Undefined function 'fftn' for input arguments of type 'int16'.

Error in fft2 (line 19)
        f = fftn(x);

Answer 1

The error message you got says it all: fft2 is not meant to work with uint16 input type.
Convert Y to double before you process it:

Y = im2double( Y );

or even just

Y = double( Y );