In order to assess in vivo deposition of CTE's tauopathy, investigators propose to use PET imaging with [F-18]FDDNP, a molecular imaging probe for PET, with high in vitro binding affinity to NFTs and of the fibrillar tau deposits as shown with fluorescent microscopy with non-radioactive FDDNP. The analysis of [F-18]FDDNP will allow investigators to evaluate the specificity and sensitivity of this imaging probe for detection of the brain pathology and utilization of these methods for detection of early deposition and for monitoring of any therapeutic intervention aimed at stopping or reducing the deposition of neuropathologic aggregates.