Table 2.
Summary of non-specific and specific PET tracer’s findings and uses in AD.
| FDG-PET | Amyloid PET | Tau PET | |
|---|---|---|---|
| Principles | Patterns of altered brain glucose metabolism | Binds amyloid-β fibrils in senile plaques | Binds paired helical filaments-tau in neurofibrillary tangles, neuropil threads, dystrophic neurites |
| Site | Hypo-metabolism in temporo-parietal cortex, and posterior cingulate (Shivamurthy and others 2014) reflecting loss of neuropil and synapse as well as functional impairment of the neurons (Ou and others 2019) | Diffuse cortical amyloid tracer binding, with predominance in frontal and posterior cingulate with a relative sparing of medial temporal cortex, occipital and sensorimotor cortex (Rowe and others 2008) | Tau tracer binding is significantly higher in the temporo-parietal cortex, and lower in subcortical regions (Lagarde and others 2019) |
| Clinical application | It can be used to support clinical diagnosis of AD (Jack and others 2018). It can also be used as a biomarker for blood-brain barrier abnormality (Sweeney and others 2019) | It can be used to establish clinical diagnosis of AD (Jack and others 2018) as well as in patient selection and evaluation of treatment response of novel anti-amyloid drugs (Okamura and others 2018) | It can be used to establish clinical diagnosis of AD (Jack and others 2018) as well as in patient’s recruitment and evaluation of treatment response in the clinical trials of the medications specifically targeting amyloid and tau (Okamura and others 2018) |
| Association with clinical severity of dementia | It can be used to measure severity of cognitive impairment and hence can be used as prognostic biomarker for AD (Mosconi and others 2009) | Little association has been established between amyloid burden and clinical severity of cognitive impairment and hence less useful as a prognostic biomarker for AD (Rabinovici and Jagust 2009) | A close relationship has been observed with tau pathology and severity of cognitive impairment and hence can be used as a prognostic biomarker for AD (Villemagne and others 2018) |
AD = Alzheimer’s disease; FDG-PET = FDG-PET = [18F]fluorodeoxyglucose–positron emission tomography.