Orateur
Description
The deeper understanding of brain activity is a major challenge for clinical and
mathematical research. In case of neurological disease, such as epilepsy, the main
objective is to better understand and diagnose the origin of the crisis in order to pro-
pose a proper treatment for each patient. Among the non-invasive imaging methods
used to study these pathologies, we are interested in the coupling of two of them :
the electroencephalography (EEG) and the diffuse optical tomography (DOT). On
one hand, the EEG measures the electrical potential generated by the neuronal ac-
tivity. On the other hand, the DOT measures the absorption and diffusion of the
light in the near-infrared spectrum by biological tissues, attesting of a change in the
concentrations of oxyhemoglobin and deoxyhemoglobin.
EEG measures the electric potential difference between a reference electrode and
electrodes placed on the scalp. There can be up to 128 electrods, arranged on a head
cap placed on the head of the patient. Regarding the DOT, it is an imaging technique
based on the absorption and diffusion of the light by the tissues. A head cap equiped
with transmitters and receivers is placed on the head of the patient. A transmitter
sends out light which is measured by the receptors after passing through the various
layers of the head. Thanks to these measurements, it is then possible to reconstruct
the optical parameters of the tissues in the head. Co-registration already exists for
these two modalities, which represents a source of motivation for the mathematical
modeling of this coupling.
In this communication, we present a time-dependent model for the acquisition of
coupled measurements of these two modalities. Indeed, time is an important com-
ponent of the neurovascular coupling. On the one hand, EEG measures the neural
activity and on the other hand, the DOT highlights the change of optical parame-
ters of brain tissues induced by the local increase in blood volume during cerebral
activity. We will also present the inverse problems associated with these two ima-
ging modalities, the inverse problem of the EEG being a source localization problem
whearas the DOT problem is a parameter identification problem. Finally, we will
explain how these modalities can be used together to improve the resolution of the
inverse problems from a numerical point of view.
