Another goal is to use the latest MRI technologies to develop specific tau imaging biomarkers that correlate with the PET and spinal fluid tau measures but without the radiation of PET or invasiveness of spinal taps. The development of these surrogate imaging markers of tau, is critically important to diagnosing CTE. This in turn will lead to studies relevant to treatment and prevention of this devastating disease. Finally, as an exploratory method of examining possible genetic risk for CTE, we will also use cutting edge genetic analysis of blood samples from subjects in this proposal and compare tau load, measured by PET tau ligand uptake and cerebrospinal fluid (CSF) p-tau level, with a measure of genetic susceptibility to tau load, referred to as the genetic risk score for tau.