Functional imaging of the human brain using a modular, fibre-less, high-density diffuse optical tomography system
Although the human brain determines all aspects of our life, signaling and signal transduction are still poorly understood. Imaging tools have been developed that facilitate real-time monitoring of changes in the brain with functional magnetic resonance imaging (fMRI) often triumphed as the tool of choice for understanding hemodynamic changes. However, MRI instrumentation is quite large and expensive to maintain. Additionally, studies on vulnerable populations such as infants and children are often not well tolerated. Diffuse optical tomography (DOT) is a novel imaging technology that can sample hemodynamic changes in the brain noninvasively, but has the distinct advantages that it is portable and light weight, facilitating imaging in nearly any population and is significantly less expensive than fMRI. In order to generate high quality hemodynamic response data from not only the surface of the cortex, but also within the brain it is imperative that a high number of optical fibers be utilized for sampling to ensure complete sampling density, resolution and field of view coverage. With this increase in sampling density, DOT systems using conventional optics have become larger and heavier, diminishing their advantages of being portable and useful in all patient populations. In the presented work, Chitnis et al have developed a fiber-less, miniaturized, silicone-encapsulated module based DOT system, known as the µNTS, that enabled three-dimensional, functional imaging of the human brain to be obtained. In their system four modules were arranged to provide up to 128, dual wavelength measurement channels over a scalp area of 60x65 mm2. The µNTS system could generate high quality DOT data in the presence of hair, which is a common difficulty faced when collecting DOT measurements on the scalp. In the presented work, robust hemodynamic responses were identified in all 5 subjects in the study, enabling reconstruction of DOT images with well-localized hemodynamic responses in all three dimensions. The system described herein paves the way for modular systems that could be part of new wearable, wireless, high-density optical neuroimaging technologies.