Yes. I agree with Margypops. My moms petscan showed degeneration.
It's my understanding the only way an Alzheimer's diagnoses can be confirmed is through an autopsy when the brain can physically examined. I know it sounds horrible (it did to me when I was first told), but unfortunately that's all we have right now.
PET images show the metabolic degeneration of the brain of a patient with Alzheimers Disease,so I would believe that the differance would be known as I have not heard of depression showing degeneration of the brain.