>Your pictures show the same coordinates in the SPECT processing tool as in the viewer after all. One is xyz and the other ijk. Ignore the Mask value.

Keep in mind that the SPECT processing tool is only valid for the MNI space, not the patient MRI. The template T1 has to be used for creating the overlay.

BTW, check out the article from Mayo, comparing SISCOM, ISAS and their new method STATISCOM (search on this term). Both of later perform about twice as well as SISCOM, but only ISAS is available to us.

You may also be interested in my PET methods. You can find it by searching YouTube for Multimodal Imaging. About to publish an article showing it is much much better than SPECT, ISAS, or conventional PET.