Spatial and temporal hemodynamic study of human primary visual cortex using simultaneous functional MRI and diffuse optical tomography

Abstract

The blood oxygenation level dependent (BOLD) functional MRI and near infrared optical tomography have been widely used to investigate the hemodynamic response to functional stimulation in the human brain. In this paper, we present a complete methodology of integrating the two imaging modalities to study the underlying physiological mechanism of hemodynamic response in the human primary visual cortex. The integration was made feasible thanks to the development of an MRI-compatible optical probe. The optical imaging was conducted using a frequency-domain near infrared spectrometer. The 3-dimentional optical image reconstruction was based on diffuse optical tomography (DOT) using the perturbative approach. The sensitivity function of the forward problem was obtained using Monte Carlo method. From our preliminary observation, the spatial activation pattern of deoxyhemoglobin is consistent with the BOLD signal map. The patterns of oxy-and deoxyhemoglobin are very similar. The temporal hemodynamic response shows an increased total hemoglobin concentration, which indicates an increment of cerebral blood volume (CBV) during physiological activation.