title: Atlas-based head modeling and spatial normalization for high-density diffuse optical tomography: in vivo validation against fMRI.
abstract: Diffuse optical imaging (DOI) is increasingly becoming a valuable neuroimaging tool when fMRI is precluded. Recent developments in high-density diffuse optical tomography (HD-DOT) overcome previous limitations of sparse DOI systems, providing improved image quality and brain specificity. These improvements in instrumentation prompt the need for advancements in both i) realistic forward light modeling for accurate HD-DOT image reconstruction, and ii) spatial normalization for voxel-wise comparisons across subjects. Individualized forward light models derived from subject-specific anatomical images provide the optimal inverse solutions, but such modeling may not be feasible in all situations. In the absence of subject-specific anatomical images, atlas-based head models registered to the subject's head using cranial fiducials provide an alternative solution. In addition, a standard atlas is attractive because it defines a common coordinate space in which to compare results across subjects. The question therefore arises as to whether atlas-based forward light modeling ensures adequate HD-DOT image quality at the individual and group level. Herein, we demonstrate the feasibility of using atlas-based forward light modeling and spatial normalization methods. Both techniques are validated using subject-matched HD-DOT and fMRI data sets for visual evoked responses measured in five healthy adult subjects. HD-DOT reconstructions obtained with the registered atlas anatomy (i.e. atlas DOT) had an average localization error of 2.7mm relative to reconstructions obtained with the subject-specific anatomical images (i.e. subject-MRI DOT), and 6.6mm relative to fMRI data. At the group level, the localization error of atlas DOT reconstruction was 4.2mm relative to subject-MRI DOT reconstruction, and 6.1mm relative to fMRI. These results show that atlas-based image reconstruction provides a viable approach to individual head modeling for HD-DOT when anatomical imaging is not available.
authors.affiliation: Department of Biomedical Engineering, Washington University, Whitaker Hall, One Brookings Dr., St. Louis, MO, 63130, USA; Department of Radiology, Washington University School of Medicine, East Bldg., 4525 Scott Ave, St. Louis, MO, 63110, USA.
authors.forename: Silvina L
authors.initials: SL
authors.lastname: Ferradal
authors.forename: Adam T
authors.initials: AT
authors.lastname: Eggebrecht
authors.forename: Mahlega
authors.initials: M
authors.lastname: Hassanpour
authors.forename: Abraham Z
authors.initials: AZ
authors.lastname: Snyder
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Culver
mesh_terms: D000328:Adult; D001271:Atlases as Topic; D001931:Brain Mapping / Q000379:methods / Q000706:statistics & numerical data; D005260:Female; D006257:Head / Q000033:anatomy & histology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods* / Q000706:statistics & numerical data; D007206:Individuality; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000706:statistics & numerical data; D008297:Male; D008953:Models, Anatomic; D017711:Nonlinear Dynamics; D010101:Oxygen Consumption / Q000502:physiology; D012016:Reference Values; D041622:Tomography, Optical / Q000379:methods* / Q000706:statistics & numerical data; D055815:Young Adult
keywords: Anatomical atlas; Brain mapping; DOI; Diffuse optical tomography; FOV; Functional magnetic resonance imaging; Group analysis; HD-DOT; HbO(2); HbR; HbT; Non-linear registration; Spatial normalization; deoxyhemoglobin; diffuse optical imaging; field of view; high-density diffuse optical tomography; oxyhemoglobin; total hemoglobin