Imaging studies have traditionally been used in the evaluation of dementia to exclude other neurological disorders such as hydrocephalus, tumors, or subdural effusions. More recently, imaging studies have focused on anatomic changes such as global or focal atrophy, ventricular or culcal enlargement or on physiological patterns of metabolism or perfusion. Among centers, there are variations in techniques and interpretations which make standardization difficult at present.

Temporal lobe and hippocampal atrophy are the most reliable anatomic findings in AD, although there is great overlap with normal aging and other dementias. Functional imaging may show changes in metabolism and perfusion which may occur before anatomic changes. When these tests are performed over the course of time, characteristic changes associated with AD may be observed. However, over the course of this time the clinical presentation has probably established the diagnosis.

CT scans and MRIs are performed even when the diagnosis is evident, usually because of family wishes.