Three-dimensional superposition of diffuse optical tomography results and subjacent anatomic structures

Abstract

Near infrared spectroscopy (NIRS) and diffuse optical tomography (DOT) reveal no information about the measurement's underlying anatomical structures. An independent anatomical mapping of DOT results onto the subject's brain or a generic brain model is desirable, especially when regions prone to large inter-subject variability are studied. We show two methods to match DOT data from high density fiber grids to anatomical structures. The forward model that is used to predict the light propagation is based on one generic anatomical MR scan. In both approaches we use this model MR-scan to translocate the position of the optical fiber grid from our experimental setup to the FEM model space. The fiducial mark approach uses the spatial normalization of the subject's MR-scan (with marked corners of the fiber grid) and the model's MR scan, leading to a translocation of the fiber pad position to the FEM-Model space. The anatomic landmark approach is used without individual MR scan. 19 reference points and the position of the fiber pad corners are determined using photogrammetry software. These coordinates are translocated to the FEM model space by solving the least square problem of the subject's and the model's reference points. We illustrate and compare both methods and show results from a vibrotactile stimulation experiment in humans.