afni.nimh.nih.gov

You could try using to3d with the TIFF files as input. Dimon is meant mostly for DICOM files, not TIFF files, but it calls to3d to do the conversion to AFNI or NIFTI format. The netpbm package must be installed too, but that's typically part of AFNI installation. Note, not all TIFF files will be readable. It's sometimes useful to use something like ImageJ/Fiji for some of the formats. You may still need to fix orientation issues afterwards in AFNI with 3drefit.