What are some options being researched to aid in diagnosing CTE with imaging?

At present, CTE is only a diagnosis that can be made postmortem and can't be diagnosed by imaging. However, researchers are making the push to attempt to diagnose CTE antemortem with the help of various imaging techniques. A study noted that magnetic resonance spectroscopy (MRS), single-photon emission computed tomography (SPECT), and diffusion tensor imaging (DTI), are currently being evaluated for their utility in the detection, classification, and prognostication in the setting of traumatic brain injury, including CTE (Shetty et al, 2016). 

DTI is an MRI technique that quantifies the direction that water diffuses in white matter tracts. Commonly studied white matter tracks include the corpus callosum, longitudinal fasciculus, cingulum bundles and uncinate fasiculus (Prabhu, 2011). This seems to be focusing on possibly picking up some of the gross pathological changes such as characteristic corpus callosum thinning (Shetty et al, 2016). However, this technique is limited in that nothing has been standardized in terms of analysis or methodology. 

Blood oxygenation level-dependent functional MRI detects changes in oxygenation of hemoglobin and correlates to brain function during task performance (Shetty et al, 2016). With increased activity comes increased cerebral blood flow and oxygenation. This could show decreased functionality through decreased oxygenation in damaged areas of the brain, that would likely go along with generalized atrophy of the brain characteristic of CTE (Shetty et al, 2016). 

Magnetic resonance spectroscopy is used to evaluate certain neurometabolites such as choline, N-acetylaspartate, creatinine and glutamine (Shetty et al, 2016). It seems as though N-acetylaspartate is linked with concussion but further research is required as sample sizes have been small. This goes along the lines of looking for biomarkers but I would posit that the specificity of this is low. Therefore, I question the ability of this method to isolate a biomarker specific to CTE. 

Overall, the diagnosis of CTE antemortem has a long way to go in terms of research and understanding. These imaging techniques have a logical basis so they seem to be good starting points.  Further study is necessary to correlate clinical and imaging findings of repetitive head injuries with the pathologic diagnosis of CTE (Shetty et al, 2016). 

Shetty T, Raince A, Manning E, Tsiouris AJ. Imaging in Chronic Traumatic Encephalopathy and Traumatic Brain Injury. Sports Health. 2016;8(1):26-36. doi:10.1177/1941738115588745.
Prabhu SP. The role of neuroimaging in sport-related concussion. Clin Sports Med. 2011;30:103-114.