Familial AD is mainly associated with mutations in PSEN1, PSEN2, and APP genes which lead to an excessive production of Aβ, or total tau (t-tau) and p-tau proteins [40, 41]. Aβ positron emission tomography is commonly used in clinical practice to quantify and localise the accumulation of Aβ in the brains of patients with AD. This evidence concerns the gene APP and Alzheimer disease.