Tau imaging with PET: an overview of challenges, current progress, and future applications.

Folded and misfolded tau is common to many neurodegenerative conditions, collectively termed "tauopathies". In recent years, many efforts have contributed toward development of tau imaging agents to allow measurement of tau deposits in vivo using positron emission tomography (PET). The particularities of tau present some unique challenges for the development of tau imaging tracers. Most notably, these pertain to the predominantly intracellular nature of tau aggregations, the existence of six isoforms, multiple post-translational modification, and that tau is usually surrounded by larger concentrations of Aβ plaques. Nevertheless, significant progress has been made towards overcoming these issues and a number of tracers are now undergoing human trials. Once validated, tau imaging with PET will be a useful tool for the differential diagnosis and disease staging, as well as therapeutic trials of AD and non-AD tauopathies.