The *6mm Res images were smoothed to 6mm uniform resolution, while the other files were smoothed to 8mm uniform resolution. For more info about the numerical data associated with those images, see ADNI_UCBerkeley_PET_8mm-to 6mm_Transformation_Methods in Study Data

There are four processed image sets that are uploaded to LONI for each ADNI PET scan. 1) (AV45)coreg, your example is for AV45, but this applied for all tracer. Coreg means the separate 5-min frames of the study have been co-registered to one another, typically the first frame. Nothing else has been done. 2) Avg, this is simply the average of the previous multiple frame upload. 3) Std Img and Vox Siz. This takes the previous image set 2, and reorients to a standard orientation, and interpolates onto a 1.5mm grid in a 160x160x96 matrtix. 4) Uniform Resolution, this is the previous image set smoothed to a given resolution. Your two lists of 4 above are the same except for what the resolution is. Originally, we used 8mm FWHM, the lowest resolution scanner (this is the last entry in your list), while a few years ago, we changes and now use a 6mm resolution. We went back in time, and for older scans that do have 6mm or better intrinsic resolution, we recalculated the Uniform 6mm resolution. So many older scans have both the 8mm and 6mm resolution. Newer scans have only the 6mm Uniform resolution upload (as no current scanners in use have lower than 6mm resolution.