If your proton density image is already in a standard space, you could use flirt with a reference image of the desired resolution. For example, to upsample an image to 2 mm voxel resolution:
flirt -ref ${FSLDIR}/data/standard/MNI152_T1_2mm -in lowres_image -out upsampled_image -applyxfm
You would also want to look at the the various options you can pass to -interp.
On Tuesday, July 10, 2012 23:55:36 you wrote:
> Drear FSL experts,
>
> I want to upsample a proton density image, how I do that? I can only find -subsamp2 but that is for downsampling, I want to have a better resolution image.
>
> Thanks,
>