Optical detection of structural alteration of brain tissues in progressive Alzheimer’s diseases using partial wave spectroscopy (PWS)

 

Alzheimer disease (AD) is the most common form of dementia, characterized pathologically by amyloid plaques and neurofibrillary tangles. One of the earliest overt signs of AD is a loss of cognitive function.  It has been reported that AD affects the nanoscale structure of the brain cells which begins long before the cognitive symptoms appear. However, these alterations are undetectable in the initial stages with currently used bulk diagnostic techniques such as MRI and OCT. Thus, the elucidation of a neuroimaging method that can uniquely characterize these structural disorders at nanoscale is imperative for clinical diagnosis. Recently developed finer-focused partial wave spectroscopy (PWS) is a sensitive technique for probing nanoscale structural alterations in cells/tissues in terms of the average structural disorder strength. Results of PWS technique measurements of brain tissues from an animal model and human subjects show significant increase in the disorder strength with the progression of AD relative to their controls. The increased disorder strength can be explained by the higher mass density fluctuations caused by the rearrangements of macromolecules due to the deposition of the amyloid beta protein and damage in DNA with progress of AD. This structural alteration may be reflected in other clinical parameters for early detection of AD and possible treatment.