Whole Head Wearable High Density Diffuse Optical Tomography
Poster No:
1981
Submission Type:
Abstract Submission
Authors:
William Hamic1, Alvin Agato1, Hannah DeVore1, Wiete Fehner1, Morgan Fogarty1, Sean Rafferty1, Dana Wilhelm1, Anthony O'Sullivan1, Calamity Svoboda1, Jason Trobaugh1, Adam Eggebrecht1, Edward Richter1, Joseph Culver1
Institutions:
1Washington University in St. Louis, St. Louis, MO
First Author:
Co-Author(s):
Introduction:
The gold standard for functional neuroimaging, fMRI, is capable of high-resolution volumetric brain imaging, but is not ideal for naturalistic imaging, as it requires confinement of the subject and is extremely motion sensitive (Eggebrecht et al., 2014). High density diffuse optical tomography (HD-DOT) imaging systems have a comparable resolution to fMRI, as their high density of optodes with overlapping measurements at different distances allows volumetric reconstructions not possible with functional near-infrared spectroscopy (fNIRS) systems (Markow et al., 2023). This positions HD-DOT as potential surrogate for fMRI, while expanding use-cases into more naturalistic contexts. Wearable DOT systems have received attention in recent years, promising to allow imaging under motion, with minimal artifacts, but systems lack sufficient optode density, an even distribution of light sources/detectors, whole head coverage, or are not sufficiently light weight for extended imaging.
We developed a light weight, fully wireless Wearable High-Density DOT (WHD-DOT) system with expanded field of view to cover primary somatosensory and motor cortex. With batteries stored in small backpack, the system it allows subject movement, from simple head motion to extended periods of walking/activity and is light enough to be worn for several hours.
We developed a light weight, fully wireless Wearable High-Density DOT (WHD-DOT) system with expanded field of view to cover primary somatosensory and motor cortex. With batteries stored in small backpack, the system it allows subject movement, from simple head motion to extended periods of walking/activity and is light enough to be worn for several hours.
Methods:
WHD-DOT (Fig. 1A) is constructed from small modules (SD-cubes) with 2 dual-wavelength LED sources and photodiode detectors each. The individually spring-loaded optodes are spaced at 13mm, (within and between SD-cubes) and evenly across the whole head, with 128 sources and 128 detectors, for 4280 total measurement channels. Time and frequency domain encoding of sources distinguishes each source and detector measurement, and control over source duty cycle (two-pass encoding) allows collection of light measurements across a high dynamic range, while maintaining an 8Hz overall framerate. SD-cube weight and size are significantly reduced from the previous iteration (Agato et al., 2023), without sacrificing system performance.
We performed in vivo testing (n=3) using a set of standard block-design localizer tasks including a flashing checkboard visual task, word hearing, verb generation and finger tapping. Head modeling was performed on MRI anatomical references, and volumetric maps of changes in oxy-hemoglobin were reconstructed using NeuroDOT. The beta values for localizers were then derived using a GLM-based approach, and analyzed with group t-maps.
We performed in vivo testing (n=3) using a set of standard block-design localizer tasks including a flashing checkboard visual task, word hearing, verb generation and finger tapping. Head modeling was performed on MRI anatomical references, and volumetric maps of changes in oxy-hemoglobin were reconstructed using NeuroDOT. The beta values for localizers were then derived using a GLM-based approach, and analyzed with group t-maps.
Results:
System characterization shows detection of very low light levels (noise-equivalent-power (NEP) of 91fW/√Hz) which allows longer/deeper measurements, while the two-pass encoding allows a high dynamic range of 151.3dB, allowing simultaneous capture of short channels. The imaging cap weighs 1820g and with a power consumption of 32.8 W, allowing multiple hours of operation. This high performance, along with low weight and power consumption is critical to attain extended length, high resolution imaging in everyday environments, as in (Fig. 1B).
T-tests of localizer maps across subjects show significant activations in regions associated with visual, auditory, language and motor tasks (Fig. 2A-E), showing system performance functions across a large field of view. This performance extends to individual trials, showing strong repeatability for short segments of data collection (Fig. 2F).
T-tests of localizer maps across subjects show significant activations in regions associated with visual, auditory, language and motor tasks (Fig. 2A-E), showing system performance functions across a large field of view. This performance extends to individual trials, showing strong repeatability for short segments of data collection (Fig. 2F).
Conclusions:
The WHD-DOT system, with whole-head field of view and fully wireless operation, is well suited for naturalistic imaging studies involving movement, including functional connectivity while walking/navigating in everyday environments and during complex motion like piano playing. Reduction of module size and weight, along with low power consumption, allows scans to occur uninterrupted for extended lengths, all while performing high-resolution whole-head imaging.
Modeling and Analysis Methods:
Methods Development 2
Novel Imaging Acquisition Methods:
NIRS 1
Keywords:
Computational Neuroscience
OPTICAL
Other - High density diffuse optical tomography; Wearables; Naturalistic stimuli; Novel imaging methods
1|2Indicates the priority used for review
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Eggebrecht, A. T., Ferradal, S. L., Robichaux-Viehoever, A., Hassanpour, M. S., Dehghani, H., Snyder, A. Z., Hershey, T., & Culver, J. P. (2014). Mapping distributed brain function and networks with diffuse optical tomography. Nature Photonics, 8(6), 448-454. https://doi.org/10.1038/nphoton.2014.107
Markow, Z. E., Trobaugh, J. W., Richter, E. J., Tripathy, K., Rafferty, S. M., Svoboda, A. M., Schroeder, M. L., Burns-Yocum, T. M., Bergonzi, K. M., Chevillet, M. A., Mugler, E. M., Eggebrecht, A. T., & Culver, J. P. (2023). Ultra-high density imaging arrays for diffuse optical tomography of human brain improve resolution, signal-to-noise, and information decoding. bioRxiv, 2023.2007.2021.549920. https://doi.org/10.1101/2023.07.21.549920