Evaluating Spatial Normalization Methods for the Human Brain
2005) Evaluating Spatial Normalization Methods for the Human Brain. MSEE, Electrical Engineering, University of Washington. (
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Cortical stimulation mapping (CSM) studies have shown cortical locations for language function are highly variable from one subject to the next. Because no two cortical surfaces are alike and language is a higher order cognitive function, observed variability is attributable to a combination of functional and anatomical variation. If individual variation can be normalized, patterns of language organization may emerge that were heretofore hidden. In order to discover whether or not such patterns exist, computer-aided spatial normalization is required. Because CSM data has been collected on the cortical surface, we believe that a surface-based normalization method will provide more accurate results than will a volume-based method. To investigate this hypothesis, we evaluate a surface-based (Caret) and volume-based method (SPM2). For our application, the "ideal" method would i) minimize variation as measured by spread reduction between cortical language sites across subjects while also ii) preserving anatomical localization of sites. Evaluation technique: Eleven MR image volumes and corresponding CSM site coordinates were selected. Images were segmented to create left hemisphere surface reconstruction for each patient. Individual surfaces were registered to the colin27 human brain atlas using each method. Deformation parameters from each method were applied to CSM coordinates to obtain post-normalization coordinates in 2D space and 3D ICBM152 space. Accuracy metrics were calculated i) as mean distance between language sites across subjects in both 2D and 3D space and ii) by visual inspection of post-normalization site locations on a 2D map. Results: Globally, we found no statistically significant difference between CARET (surface-based method) and SPM2 (volume-based method) as measured by both spread reduction and anatomical localization. Local analysis showed that more than twenty percent of total mapping errors were mapped incorrectly by both methods. There was a statistically significant difference between Caret and SPM2 mapping of type 2 errors.
|Keywords:||brain functional imaging spatial normalization cerebral cortical mapping neural engineering evaluation methodology|
|Projects:||Human Brain Project|
|Deposited By:||Martin, Richard F|
|Deposited On:||06 May 2005|