title: Image registration of two volume with different number of slices
body: <p>I am trying to register two volumetric images from brain (PET and CT or even PET and MR). Each of these volumetric images contains different numbers of 2D images (slices). 
  For example, <code>CT</code> has <code>150</code> slices and <code>PET</code> has <code>100</code> slices. I was thinking of using an interpolation method to calculate and reduce the number of CT slices to 100. Is this a correct approach? Does anyone know of any resources that could be helpful for me? like a pseudo code, or steps that I should go through for registering two volumetric images.
  Thank you :)</p>