Extended hierarchical Bayesian diffuse optical tomography for removing scalp artifact

Abstract

Abstract:Functional near-infrared spectroscopy (fNIRS) can noninvasively measure hemodynamic responses in the cerebral cortex with a portable apparatus. However, the observation signal in fNIRS measurements is contaminated by the artifact signal from the hemodynamic response in the scalp. In this paper, we propose a method to separate the signals from the cortex and the scalp by estimating both hemodynamic changes by diffuse optical tomography (DOT). In the inverse problem of DOT, we introduce smooth regularization to the hemodynamic change in the scalp and sparse regularization to that in the cortex based on the nature of the hemodynamic responses. These appropriate regularization models, with the spatial information of optical paths of many measurement channels, allow three-dimensional reconstruction of both hemodynamic changes. We validate our proposed method through two-layer phantom experiments and MRI-based head-model simulations. In both experiments, the proposed method simultaneously estimates the superficial smooth activity in the scalp area and the deep localized activity in the cortical area.

Diffuse optical tomography using multi-directional sources and detectors

“…The regularization effect becomes dominant as the absorption change is located in a deeper area, since the observed light-intensity change weakens with depth relative to the regularization effect. The same phenomenon was also observed in our previous study [20]. The above results of the simulation experiment showed that multi-directional DOT was accurate up to a 15-mm depth.…”

“…Thus, visualization by multidirectional DOT is limited to areas around the cortical surface. By contrast, because many distinct optical paths exist in a shallow area enough to reconstruct a three-dimensional image, it would be possible to utilize such a method that reconstructs a scalp's hemodynamic change as well as a cortical hemodynamic change and remove the former [9,10,20]. The results also show that estimation was difficult in the distant area of the rectangular arrangement (Fig.…”

“…4(a). These black dots indicating the center position of the absorber were located at intervals of 2.5 mm in a cuboid represented by the dotted line whose boundary is x = [-15,15], y = [0,15], z = [5,20] [mm]. The total number of absorber locations was 105.…”

Time–frequency dynamics of the sum of intra- and extracerebral hemodynamic functional connectivity during resting-state and respiratory challenges assessed by multimodal functional near-infrared spectroscopy

“…Future work is needed to quantify the impact of extracerebral hemodynamic changes on fNIRS signals as well as to develop appropriate methods to reduce this confounding factor. Useful approaches were already developed (e.g., [Berger et al, 2012;Gagnon et al, 2014;Haeussinger et al, 2014;Jelzow et al, 2014;Saager et al, 2011;Saager and Berger, 2008;Scarpa et al, 2013;Shimokawa et al, 2013;Tanaka et al, 2013;Yamada et al, 2012;Zucchelli et al, 2013]) that could be used for future fNIRS studies about similar aspects as analyzed in the present study.…”

State-space models of impulse hemodynamic responses over motor, somatosensory, and visual cortices

“…In recent years, functional near-infrared spectroscopy (fNIRS) has been used as an alternative non-invasive brain imaging technique to fMRI [10][11][12][13][14][15]. fNIRS determines the concentration changes of oxy-hemoglobin (HbO) and HbR in tissues by measuring lightabsorption variations at multi-wavelengths [16].…”