Anatomic and physiologic imaging of Alzheimer's disease

At present, no imaging modality is considered the standard diagnostic test for AD. On anatomic studies, severity of temporal lobe and hippocampal atrophy are the most reliable findings in AD, although overlap of these findings among AD, aging, and other dementias mitigate the value of these measures for application to the individual case. Although somewhat cumbersome for routine use, quantitative MR measurements offer more precise comparison of degrees of atrophy. Functional imaging may demonstrate abnormalities of perfusion or metabolism that precede anatomic changes (PET, SPECT, or MRS), yet these techniques generally require additional anatomic information from MR for interpretation. Newer investigational MR techniques such as MRS and functional MR in combination with conventional MR imaging have the potential to combine metabolic with anatomic imaging in one examination. A combination of both metabolic and anatomic imaging studies may ultimately offer better sensitivity and specificity for diagnosis, monitoring, and follow-up of AD.