This pilot study aims to assess if participants that meet the criteria for a TES diagnosis have a specific tau deposition profile on PET scanning using the PET tau binding ligand - [18F] PI-2620. It is hoped this study will highlight potential diagnostic tests of TES diagnosis, the in-life correlate of CTE.

Inclusion Criteria:

• The participant must have full capacity to understand the purpose and risks of the study to provide informed consent.
• All participants must be between 40 to 70 years of age.
• Must meet the Traumatic Encephalopathy Syndrome criteria as defined by the National Institute of Neurological Disorders and Stroke Consensus Diagnostic Criteria for Traumatic Encephalopathy Syndrome, Katz. D, et. al. Neurology, 2021.
• Participants must demonstrate that they have a cognitive decline, evident by performance on neuropsychological testing.
• Standard of care blood screening within 12 months of consent to the study to exclude other medical conditions which may cause cognitive decline, such as heavy metal toxicology.
• A PET scan within 6 months of consent to the study that is not consistent with Alzheimer's disease.
• Participants must consent to undertake Positron Emission Tomography (PET) with intravenous [18F] PI-2620 PET tracer ligand.
• Participants must be able to lie still, on their back for up to 60 minutes for the scans.
• Participants must not have any metal in their bodies e.g. pacemakers, aneurysm clips which are contraindications of MRI.
• Participants must consent to the use of their medical records and medical history, including but not limited to pathology results, previous imaging results and neuropsychology results

Exclusion Criteria:

• Participants will be excluded if they do not meet all the inclusion criteria.
• Participants must not be diagnosed with or suspected to be suffering from any other neurodegenerative disease, or cerebral disease affecting cognition as identified by results of neuropsychological evaluation or neurologist consultation.
• Participants will be excluded if Staff at Macquarie Medical Imaging determine that the participant is not suitable for imaging, for any reason.
• Participants will be excluded if they have kidney and/or liver dysfunction as diagnosed by a doctor