Alzheimer's disease: Potential pathogenesis and imaging findings

Alzheimer's disease (AD) is a common neurodegenerative disease. The histopathological changes in AD include amyloid beta-protein (A beta) deposition, tau tangles, neuroinflammation, and neurodegeneration. Some of the pathological changes could be shown in vivo by positron emission tomography (PET) and magnetic resonance imaging (MRI) biomarkers, which play a key role in diagnosing AD. Fluorodeoxyglucose positron emission tomography (FDG-PET) can reflect and predict dysfunction. A beta-PET is sensitive for the diagnosis of early AD but cannot distinguish the severity of AD. Tau-PET can compensate for the deficiency of A beta-PET. Tau tangles are positively correlated with the severity of AD and associated with cognitive impairment. Probes targeting neuroinflammation in AD have been developed, but further study is needed to validate their effectiveness. Conventional MRI performs high tissue contrast that can show structural changes and has been routinely applied in clinical practice, such as in the evaluation of cerebral atrophy. Advanced MRI sequences (such as diffusion tensor imaging, arterial spin labeling, magnetic resonance spectroscopy, blood oxygenation level dependent, and quantitative susceptibility mapping) can provide additional information beyond structure that includes brain microstructure, blood perfusion, metabolite concentration, brain activity, connections and networks between brain regions, iron deposition, etc. Integrated PET and MRI may improve the diagnostic efficiency of AD.