Diffuse optical cortical mapping using the boundary element method

Abstract

Cortical mapping, also called optical topography is a new medical imaging modality which allows the non-invasive investigation of the outer layers of the cortex. This technique is challenging and the geometry of the subject is very often over-simplified. We aim here to localize activated regions of an anatomically accurate brain. A Boundary Element Method is used for the forward model. The reconstruction of perturbations in the absorption coefficient is demonstrated in a geometrically realistic simulation and in vivo. These results show that diffuse optical imaging of the head can provide reliable activity maps when anatomical data is available.

Keywords: (110.0113) Imaging through turbid media; (110.3200) Inverse scattering; (170.3010) Image reconstruction techniques.

Fig. 1.

Left to right and top to bottom, reconstructions of a Gaussian absorption target simulated with the FEM (1% noise). The target is moved by 2mm from the surface of the brain (top left) to 20mm below the surface.

Fig. 2.

Evolution of the contrast, i.e. the difference absorption of the target divided by the background absorption. The nominal value is 1.43.

Fig. 3.

Side and top views of a cortical map of the activated brain - the primary motor and somatosensory cortices activation is clearly visible. This position corresponds to the arm region as it can be seen in [45].