Team Asclepios

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Section: Other Grants and Activities

Foreign associated team

Participants : Xavier Pennec [ Correspondant ] , Vincent Arsigny, Pierre Fillard, Nicholas Ayache, Caroline Brun [ LONI, UCLA ] , Natasha Lepore [ LONI, UCLA ] , Paul Thompson [ LONI, UCLA ] .

Since its creation in September 2001, the associated team program between the Asclepios laboratory at INRIA and the laboratory of NeuroImaging at the UCLA School of Medicine has enabled an active collaboration between both structures, with the objective of comparing and analyzing the performances and behaviors of image processing algorithms devoted to the building of brain atlases.

Since 2004, we study the anatomical variability of the brain, in the framework of the PhD thesis of P. Fillard. Our strategy is to construct a statistical model of manually delineated landmarks at the surface of the cortex: sulcal lines. The mean sulcal lines are determined by iteratively optimizing over the position of the mean line and the matchings with all the instances. Then, covariance matrices are computed on each lines independently and then diffused in the whole space thanks to the log-Euclidean framework. This year, the results previously obtained with the statistical model of 72 sulcal lines were extended to take into account the influence of the spatial affine normalization and the number of tensors picked as model parameters. The results were published in [42] (see also Section 6.4.3 ). Another publication is currently prepared with P. Thompson on the neuroscientific interpretations of the results on the brain asymmetry obtained with new statistical methods to probe the co-variability of symmetrical points.

Following the visit of A. Leow in January 2006 and N. Lepore in June 2006, a new collaboration axis was initialized on tensor based morphometry. The goal is to perform statistics on the Cauchy-Green Tensor of deformations between subjects [128] using the log-Euclidean [33] or the affine invariant metric [50] and to reuse these statistics as a regularization criterion for non-linear image registration [86] . A working meeting between X. Pennec, N. Lepore and C. Brun (PhD student at UCLA) was held on this subject at the MICCAI and MFCA conferences in Copenhagen in October, and several articles are currently under way.

P. Thompson, X. Pennec, N. Ayache participated to the Symposium ISBI'06 in Washington DC, USA, April 06. X. Pennec, N. Ayache, P. Fillard, C. Brun and N. Lepore participated to the MICCAI'06 conference in Copenhagen, Denmark, October 2006. X. Pennec organized the first workshop on the Mathematical Foundations of Computational Anatomy on October 1st at Copenhagen. V. Arsigny, P. Fillard, N. Lepore et C. Brun did participate to this event with presentations related to the associated team themes by V. Arsigny, N. Lepore and X. Pennec. X. Pennec presented results from the associated team program at invited talks at the Shape Space workshop at the Institute for Mathematics and Applicatioons (IMA, Minneapolis, USA) in April 2006, at Jonhs Hopkins University, and at the 15th ERNSI workshop on system identification, Linkoping, Sweden, septembre 2006.


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