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PET study shows superiority of Tau imaging in predicting brain atrophy in early Alzheimer’s disease

Wednesday 01 January 2020

On 1 January, Dr Renaud La Joie and colleagues published a paper in Science Translational Medicine, showing that tau-PET imaging is a more accurate predictor than amyloid-PET imaging of subsequent brain atrophy in early Alzheimer’s disease (AD). Positron emission tomography (PET) uses radioactive dyes (also known as tracers) that stick to specific molecules in the body, revealing their presence on PET scans.  For example, amyloid tracers such as [18F] Florbetapir can be used to detect the presence and extent of amyloid plaques in the brain, facilitating a more accurate diagnosis of AD. However, amyloid-PET studies have shown little association between amyloid burden and the clinical severity of dementia. It is not yet known whether Tau-PET can more accurately predict neurodegeneration in people with AD, as Tau-PET imaging is a relatively novel technique. 

To answer this question, Dr La Joie and colleagues undertook a PET imaging study in a group of 32 people with early symptomatic AD, comparing the ability of amyloid-PET or Tau-PET to predict brain atrophy as measured by structural MRI (magnetic resonance imaging). Using the imaging data from PET and MRI scans, they generated 3D maps showing the topography of brain atrophy in relation to amyloid-PET or Tau-PET signals. Looking at baseline levels of Tau-PET, they found a strong association with subsequent brain atrophy, suggesting that aggregation of Tau in neurofibrillary tangles is a good predictor of future neurodegeneration. In comparison, amyloid-PET performed poorly, showing a low association of amyloid accumulation with brain atrophy.

The researchers also evaluated whether age at baseline was associated with the quantity of amyloid or Tau detected on PET scans. They observed that individuals who were diagnosed at an older age tended to have less Tau accumulation – and slower rates of brain atrophy.  Conversely, earlier onset of AD was associated with a higher baseline Tau burden, and more rapid atrophy. To confirm the results of this study, more large-scale investigations involving additional disease stages and longer follow-up durations are now required.

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