Functional imaging of the human brain using a modular, fibre-less, high-density diffuse optical tomography system.

Danial Chitnis,Nicholas L Everdell,Laura Dempsey,Clare Elwell,David Highton,Samuel Powell,Jeremy C Hebden,Robert J Cooper,Simone Quaggia

doi:10.1364/boe.7.004275

Abstract

We present the first three-dimensional, functional images of the human brain to be obtained using a fibre-less, high-density diffuse optical tomography system. Our technology consists of independent, miniaturized, silicone-encapsulated DOT modules that can be placed directly on the scalp. Four of these modules were arranged to provide up to 128, dual-wavelength measurement channels over a scalp area of approximately 60 × 65 mm2. Using a series of motor-cortex stimulation experiments, we demonstrate that this system can obtain high-quality, continuous-wave measurements at source-detector separations ranging from 14 to 55 mm in adults, in the presence of hair. We identify robust haemodynamic response functions in 5 out of 5 subjects, and present diffuse optical tomography images that depict functional haemodynamic responses that are well-localized in all three dimensions at both the individual and group levels. This prototype modular system paves the way for a new generation of wearable, wireless, high-density optical neuroimaging technologies.

Highlights

Diffuse optical tomography (DOT) is an extension of near-infrared spectroscopy (NIRS) [1] in which multiple sources and detectors of near-infrared light are arranged so as to provide a wide range of source-detector separations and overlapping spatial sampling of the target object [2]
We present the first three-dimensional, functional images of the human brain to be obtained using a fibre-less, high-density diffuse optical tomography system
We identify robust haemodynamic response functions in 5 out of 5 subjects, and present diffuse optical tomography images that depict functional haemodynamic responses that are well-localized in all three dimensions at both the individual and group levels

Summary

Introduction

Diffuse optical tomography (DOT) is an extension of near-infrared spectroscopy (NIRS) [1] in which multiple sources and detectors of near-infrared light are arranged so as to provide a wide range of source-detector separations and overlapping spatial sampling of the target object [2]. When applied to the human scalp, DOT can be used to produce three-dimensional maps of changes in the concentration of the principal absorbers of near-infrared light in the human tissues, namely the oxygenated and de-oxygenated forms of haemoglobin [3] It is this capacity to non-invasively image cerebral haemodynamics (and to do so using relatively inexpensive, portable equipment) that makes continuous-wave DOT a highly effective technology for functional imaging of the human brain [4,5]. While DOT has numerous advantages, its uptake as a functional neuroimaging methodology has been limited by several fundamental challenges These include the technique’s high sensitivity to haemodynamics in the superficial, extra-cerebral tissues [6] and the necessity of obtaining appropriate anatomical spatial priors for optical image reconstruction. The greatest limiting factor in the acceptance of DOT as a functional neuroimaging method has been the need to balance the competing factors of sampling density, resolution, field-of-view and the practical challenge of applying high numbers of optical fibre bundles to the scalp of a subject [12]

Methods

Results

Conclusion