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## Section: New Results

### 3D registration for correlative light-electron microscopy

Participants : Bertha Mayela Toledo Acosta, Patrick Bouthemy.

Correlative light and electron microscopy (CLEM) enables the study of cells and subcellular elements in complementary ways by combining information on the dynamics and on the structure of the cell, provided a reliable registration between light microscopy (LM) and electron microscopy (EM) images is efficiently achieved. We have developed a general automatic registration method. Due to large discrepancies in appearance, field-of-view, resolution and position, a pre-alignment stage is required before any 3D fine registration stage. We first compute a 2D maximum intensity projection (MPI) of the LM stack along the $z$-axis, and we match 2D EM regions of interest (ROI), extracted from different EM slices, into the 2D LM-MPI image. From the resulting candidates, we estimate, using a robust criterion, the 2D $xy$-shift to pre-align the LM and EM stacks. Afterwards, a 3D affine transformation between 3D-LM-ROI and 3D-EM–ROI can be estimated using mutual information. We carried out experimental results on different real datasets of 3D correlative microscopy, demonstrating computational efficiency and overlay accuracy.

Collaborators: Xavier Heiligenstein (UMR 144 CNRS-Institut Curie),

Grégoire Malandain (Inria, Morpheme EPC, Sophia-Antipolis).