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Normalisation des données

Normalisation des données. Oury Monchi , Ph.D . Centre de Recherche, Institut Universitaire de Gériatrie de Montréal & Université de Montréal. Stereotaxic Space.

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Normalisation des données

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  1. Normalisation des données OuryMonchi, Ph.D. Centre de Recherche, Institut Universitaire de Gériatrie de Montréal & Université de Montréal

  2. Stereotaxic Space J. Talairach and P. Tournoux, Co-planar stereotactic atlas of the human brain: 3-Dimensional proportional system: an approach to cerebral imaging, Stuttgart, Georg Thieme Verlag, 1988 • based on anatomical landmarks (anterior and posterior commissures) • originally used to guide blind stereotaxic neurosurgical procedures (thalamotomy, pallidotomy) • now used by NeuroScientific community for interpretation and comparison of results

  3. AC-PC line posterior commissure AC-PC line anterior commissure VAC

  4. Stereotaxic Space J Talairach & P Tournoux, Co-planar stereotaxic atlas of the human brain, Georg Thieme, 1988

  5. Stereotaxic Space

  6. Anatomical variability remains Talairach & Tournoux Atlas, 1988 variability of central sulcus from 20 subjects

  7. Not Registered Data Images courtesy A. Zijdenbos, MNI

  8. Registered Data

  9. Registration to Stereotaxic Space Advantages for anatomical/structural imaging: • facilitates comparisons across • time points • subjects • groups • sites • permits averaging between subjects to S/N • Allows the use of spatial masks for post-processing (anatomically driven hypothesis testing) • allows the use of spatial priors (classification) • allows the use of anatomical models (segmentation) • provides a framework for statistical analysis with well-established random field models • Allows the rapid re-analysis using different criteria

  10. Registration to Stereotaxic Space Advantages for functional imaging: • Provides a conceptual framework for the completely automated, 3D analysis across subjects. • Facilitate intra/inter-subject comparisons across • time points, subjects, groups, sites • Extrapolate findings to the population as a whole • Increase activation signal above that obtained from single subject • Increase number of possible degrees of freedom allowed in statistical model • Enable reporting of activations as co-ordinates within a known standard space • e.g. the space described by Talairach & Tournoux

  11. Talairach Atlas Drawbacks for functional imaging: • is derived from an unrepresentative single 60-yr old female cadaver brain (when most functional activation studies are done on young living subjects!) • ignores left-right hemispheric differences • has variable slice separation, up to 4mm • while it contains transverse, coronal and sagittal slices, it is not contiguous in 3D

  12. Stereotaxic Space However, the space and the stereotaxic concept are still worthwhile: • Provides a conceptual framework for the completely automated, 3D analysis across subjects. • Collins, L., Evans A., et al. have created a replacement target volume for stereotaxic mapping to address weaknesses of the Talairach atlas

  13. Image Registration • Registration - i.e. Optimise the parameters that describe a spatial transformation between the source and reference (template) images • mritotal: créer la matrice de transformation .xfm • Transformation - i.e. Re-sample according to the determined transformation parameters • p.ex: mincresampleouresample_tal: appliquer la • transformation aux données

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