High density diffuse optical tomography (HD-DOT) combines logistical advantages of fNIRS with enhanced image quality, validated extensively against fMRI in adults and neonates. However, HD-DOT is yet to be evaluated in preschool-age children. Here we present an HD-DOT system optimized for preschoolers, including a 128-source by 125-detector console, light-weight fiber optics, and an expanded field-of-view. We validated the system by mapping cortical activations during visual, auditory, and motor tasks in adults. We then imaged children while they watched movies, finding reproducible patterns of brain activity and showing that feature regressors can map functionally specific regions from movie-viewing data in preschoolers.
Though optical imaging of human brain function is gaining momentum, widespread adoption is restricted in part by a tradeoff among cap wearability, field of view, and resolution. To increase coverage while maintaining functional magnetic resonance imaging (fMRI)-comparable image quality, optical systems require more fibers. However, these modifications drastically reduce the wearability of the imaging cap. The primary obstacle to optimizing wearability is cap weight, which is largely determined by fiber diameter. Smaller fibers collect less light and lead to challenges in obtaining adequate signal-to-noise ratio. Here, we report on a design that leverages the exquisite sensitivity of scientific CMOS cameras to use fibers with ∼30 × smaller cross-sectional area than current high-density diffuse optical tomography (HD-DOT) systems. This superpixel sCMOS DOT (SP-DOT) system uses 200-μm-diameter fibers that facilitate a lightweight, wearable cap. We developed a superpixel algorithm with pixel binning and electronic noise subtraction to provide high dynamic range (>105), high frame rate (>6 Hz), and a low effective detectivity threshold (∼200 fW / Hz1/2-mm2), each comparable with previous HD-DOT systems. To assess system performance, we present retinotopic mapping of the visual cortex (n = 5 subjects). SP-DOT offers a practical solution to providing a wearable, large field-of-view, and high-resolution optical neuroimaging system.