A method of determining the degree of uptake of a PET maker in an individual candidate PET scan, the method including the steps of: (a) calculating a series of representative matched controlled PET and MRI templates for a series of controlled sample scans of individuals; (b) computing a series of brain surfaces from the matched templates; (c) aligning the individual candidate PET scan with the candidate templates; (d) aligning the candidate PET images with the series of brain surfaces; (e) selecting a predetermined (M) best candidate templates for each surface location based on a similarity measure between the candidate PET values and the corresponding controlled PET scans; (f) computing M weights for each surface location, utilizing a corresponding MRI tissue map; (g) utilizing the M weights to combine a corresponding M template tissue indicators from corresponding MRI templates into an average brain surface indicator.