Axonal injury is a leading factor in neuronal injuries such as mild traumatic brain injury (TBI), multiple sclerosis (MS), Alzheimer's Disease/dementia (AD), among other disorders.  In addition, abnormal functional connectivity exists in these neuronal disorders as well as others, such as post-traumatic stress disorder (PTSD).  Neuroimaging tools have been used for diagnosing neurological and psychiatric disorders, e.g., including TBI, PTSD, AD, autism, MS, and schizophrenia.  For example, neuroimaging techniques such as X-radiation (X-ray), X-ray computed tomography (CT), magnetic resonance imaging (MRI), and diffusion tensor imaging (DTI) have been employed. 
Many of these neuroimaging techniques mainly focus on detecting blood products, calcification, and edema, but are less sensitive to axonal injuries and abnormal functional connectivity in the brain.  For example, X-ray, CT, and MRI can have relatively low diagnostic rates to these neurological and psychiatric disorders.  For example, less than 10% of mild TBI patients have shown positive findings in X-ray, CT, and MRI.  Some techniques such as diffusion tensor imaging (DTI) have shown to produce a positive finding rate ˜20-30% for mild TBI.