Both Aβ and phosphorylated tau are traditional biomarkers for other disorders and can be detected in vivo or in vitro. Scanning tunneling microscopy detects Aβ in vitro, and the two-photon Rayleigh scattering assay technique can be used to detect tau. In vivo, Aβ plaques can be detected using mMRI and optical/fluorescent imaging . Furthermore, biomarkers indicating neurological injury include the hippocampal volume or atrophy of the medial temporal lobe on MRI, as well as temporoparietal/precuneus hypometabolism or hypoperfusion on positron emission tomography or single-photon emission computerized tomography . Recent studies have detected elevated levels of Aβ and abnormal tau in neocortical regions , with decreased volumes observed in the left precuneus, superior temporal gyrus, and fusiform gyrus on MRI studies . Family and population studies suggest that individuals with the fourth form of the Apolipoprotein E gene on chromosome 14 have an increased risk of developing AD, whereas carriers of types 2 and 3 of this gene are not affected. Individuals aged between 65 and 75 are also at a higher risk of developing AD . In several recent studies, a-synuclein has been detected in the cerebrospinal fluid of patients with AD or Parkinson's disease, which may be correlated with other biochemical biomarkers .