Peering inside the mind: Imaging brain activity with advanced diffuse optical tomography

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Science Translational Medicine  12 Oct 2016:
Vol. 8, Issue 360, pp. 360ec162
DOI: 10.1126/scitranslmed.aai9158

Brain imaging has become central to a host of research and clinical applications, from magnetic resonance imaging (MRI) investigations of consciousness and thought to traumatic brain injury diagnostics. Functional brain imaging can interrogate activity and quantify processes in a spatiotemporal manner throughout the brain and is therefore useful across many clinical and research settings. Functional MRI has been a core research tool in this field, giving researchers and clinicians the ability to map activity throughout the adult brain.

Diffuse optical tomography (DOT) is an optical spectroscopy technology that uses light to monitor brain activity. Light can undergo multiple scattering events after entering the tissue, with some photons redirected back towards the tissue surface. The distance this light travels, as well as changes in its intensity and spectrum, carries information that can be decoded to measure events (e.g., absorption) and map their locations within tissue. Some of the first applications using this toolkit to capture brain activity measured hemodynamics via the detection of oxygenated and deoxygenated hemoglobin through the intact skull using red and near-infrared light.

Now, Chitnis et al. introduced a new DOT method for imaging brain activity that makes use of a fine meshwork of multiple miniature LED and detector modules. The combination of four modules yields 128 channels over a wide area of the scalp, providing the spatial resolution to map the 3D localization of hemodynamic changes. When subjects performed a thumb-to-finger extension movement, the module system was able to visualize the activated region within the motor cortex by detecting changes in hemoglobin oxygenation. The authors noted that while this measurement was made with four modules, their current method could be scaled theoretically to 75 modules for imaging over the entire scalp. Unlike functional MRI machines, this imaging system is lightweight and highly portable, which has the potential to enable wearable, functional brain imaging in office, field, and low-resource settings.

D. Chitnis et al., Functional imaging of the human brain using a modular, fibre-less, high-density diffuse optical tomography system. Biomed. Opt. Express 7, 4275–4288 (2016). [Full Text]

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