Imagine having to spot a single grain of cereal at the bottom of a bowl of milk. Now imagine a neuroscientist or physician having to peer through turbid brain tissue in search of a sick cell. The problem in either case is the same: light scatters. Just as tiny fat goblets in milk randomly redirect photons to give milk its white appearance, the estimated 100 billion nerve cells and 100 trillion synapses that store information, along with 400 miles of blood vessels, obscure our view of the brain below the cortical surface. Right now, tools to visualize this intricate mesh of cells, axons, dendrites and blood vessels are inadequate to make sense of the brain’s complexity.
Yet what if light scattering could be used to our advantage? We recently set out to explore this possibility by adapting an imaging method known as Optical Coherence Tomography (OCT). An optical version of ultrasound, OCT involves shining a light on a biological specimen and measuring how much light is reflected or scattered back. The strength and timing of these light “echoes” as they bounce off various tissue types and return to a detector are used to construct a three-dimensional picture. OCT is already used clinically in ophthalmology to make retinal images for diagnosing disease, albeit with shorter wavelengths. We hope that OCT will ultimately contribute to a better understanding of brain diseases such as traumatic brain injury, vascular dementia and Alzheimer’s disease.