Exploring the Utility of [18F]3F4AP for Demyelination Imaging in Controls, Neurodegeneration and Traumatic Brian Injury

The overall objective is to obtain an initial assessment of the value of using \[18F\]3F4AP for imaging demyelinating diseases such as traumatic brain injury (TBI), neurodegenerative diseases such as mild cognitive impairment (MCI) and Alzheimer's Disease (AD): * Aim 1) Assess the safety of \[18F\]3F4AP in healthy volunteers and subjects with traumatic brain injury (TBI) and neurocognitive impaired subjects (AD/MCI). Hypothesis 1: Administration of \[18F\]3F4AP will result in no changes in vitals or other adverse events. * Aim 2) Assess the radiation doses to the main organs in healthy volunteers. Hypothesis 2: the radiation doses to each organ will be comparable in all subjects and within the acceptable limits. * Aim 3) Assess the pharmacokinetics of a bolus infusion of \[18F\]3F4AP in humans including healthy volunteers and patients. Hypothesis 3: the pharmacokinetics of \[18F\]3F4AP at the whole brain level will be similar in controls, TBI and AD/MCI subjects. The kinetics in demyelinated lesions will be slower than in healthy areas. * Aim 4) Correlate MR images with \[18F\]3F4AP PET images. Hypothesis 4A: all the lesions seen on the MRI will show increased signal (VT or SUV) on the PET images. Hypothesis 4B: some of the lesions on the MRI will show increased signal (VT or SUV) on the PET but not all. * Aim 5) Correlate \[18F\]3F4AP PET signal with neuropsychological testing in people with TBI and AD/MCI. Hypothesis 5A: increased PET signal (VT or SUV) will correlate with impaired Mini Mental State Examination (MMSE).