Hello,

 So, after typing V= spm_vol ('bold_001.img'),  I've got answers  as following.

 ans =
        
         filename: 'bold001.img'
         dim : [80 80 36 4]
         mat : [4X4 double]
      pinfo  : [3X1 double]
      
                  .
                  .
                  .

 I looked up the help spm_vol and they explain that each number in dim is about x, y, and z dimensions of the volume, and the data type of the image.
 I wonder what the scale is (i.e., mm, cm) and what 4 means in the 4th column?
 Also, if I type V.pinfo, I get answer    1
                                                       0
                                                       0
 Can any one tell me what each number means?

 

 Thanks!!