Fluorodeoxyglucose Positron Emission Tomography (FDG PET) and Magnetic Resonance Imaging (MRI) are commonly used in a clinical setting as an examination in Alzheimer’s Disease (AD) patients. FDG PET is an imaging tool to evaluate hypometabolism; meanwhile, the MRI observes the brain volume. However, it is still unclear which examination better reflects the tau tangles, which have been known as the hallmark’s pathology of AD. Therefore, this study was conducted to compare FDG PET and MRI in assessing tau pathology in AD, by utilizing a database from the Alzheimer’s Disease Neuroimaging Initiative (ADNI). The presence of tau tangles was confirmed by using the Tau-PET images. In total, 275 cognitively impaired subjects were included as well as a subgroup of 147 subjects with positive amyloid status. Based on the analysis, it was observed that higher Tau-PET is significantly associated with FDG PET hypometabolism and MRI atrophy. A similar result was also seen in the amyloid positive subgroups. By comparing the spearman’s correlation coefficients, it was found that that the correlation was stronger between Tau PET and FDG PET (r=-0.414, p<0.001, and r=-0.475, p<0.001 in the positive amyloid subgroup) compared to Tau-PET and MRI (r=-0.331, p<0.001 and r=-0.440, p<0.001 in the positive amyloid subgroup). Inconclusion, FDG PET better reflects the tau pathology compared to MRI in AD.

Background Corticobasal syndrome is associated with cerebral protein aggregates composed of 4-repeat (~50% of cases) or mixed 3-repeat/4-repeat tau isoforms (~25% of cases) or nontauopathies (~25% of cases). Objectives The aim of this single-center study was to investigate the diagnostic value of the tau PET-ligand [18F]PI-2620 in patients with corticobasal syndrome. Methods Forty-five patients (71.5 ± 7.6 years) with corticobasal syndrome and 14 age-matched healthy controls underwent [18F]PI-2620-PET. Beta-amyloid status was determined by cerebral β-amyloid PET and/or CSF analysis. Subcortical and cortical [18F]PI-2620 binding was quantitatively and visually compared between β-amyloid-positive and -negative patients and controls. Regional [18F]PI-2620 binding was correlated with clinical and demographic data. Results Twenty-four percent (11 of 45) were β-amyloid-positive. Significantly elevated [18F]PI-2620 distribution volume ratios were observed in both β-amyloid-positive and β-amyloid-negative patients versus controls in the dorsolateral prefrontal cortex and basal ganglia. Cortical [18F]PI-2620 PET positivity was distinctly higher in β-amyloid-positive compared with β-amyloid-negative patients with pronounced involvement of the dorsolateral prefrontal cortex. Semiquantitative analysis of [18F]PI-2620 PET revealed a sensitivity of 91% for β-amyloid-positive and of 65% for β-amyloid-negative cases, which is in excellent agreement with prior clinicopathological data. Regardless of β-amyloid status, hemispheric lateralization of [18F]PI-2620 signal reflected contralateral predominance of clinical disease severity. Conclusions Our data indicate a value of [18F]PI-2620 for evaluating corticobasal syndrome, providing quantitatively and regionally distinct signals in β-amyloid-positive as well as β-amyloid-negative corticobasal syndrome. In corticobasal syndrome, [18F]PI-2620 may potentially serve for a differential diagnosis and for monitoring disease progression. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society