From Vesalius to tractography.

The description of an anatomical specimen may look straightforward, but it appears that it depends in fact on several intermingled factors: technical methods for conservation, dissection and vascular injection and the anatomist skills are of course important. This is especially true when the studied organ, as for instance the brain, is subject to rapid putrefaction after death without any preservation technique. Nevertheless the possibility to reject, or at least criticize, the dominant paradigm is probably as important as these technical considerations: important changes occurred in brain representation between the early Middle Ages and the Early Modern Times, without major improvements of cadaveric preservation or dissection methods; Vesalius rejected the existence of the rete mirabile in human not only because he was a talented anatomist but also because he accepted and had the courage to fight the dominant tradition inherited from Galen. Such difficulties in the scientific approach obviously remain vivid, and should not be forgotten despite the development of modern tools for studying brain morphology and function.

The choroidal fissure: anatomy and surgical implications.

The choroidal fissure (CF) is an important landmark that allows approaches to the deepest aspects of the brain. It is the C-shaped site of attachment of the choroid plexus in the lateral ventricles, which runs between fornix and thalamus. The thinness and the absence of neural tissue between the ependyma and pia matter of this part of the medial wall of the lateral ventricles provides a surgical pathway to the third ventricle and perimesencephalic cisterns. A precise knowledge of the microsurgical anatomy of the region, particularly vascular relationships, is essential to consider surgery through the CF. We decided to present the anatomy of the CF in three distinct chapters, corresponding to three compartments of the C-shaped structure of the CF. In each compartment - rostral, dorsal and caudal - we developed the neurovascular anatomy and then discussed the clinical and surgical applications.

Acquisition and interactive 3D exploration of the internal structure of a dissected specimen.

We present a system to keep track of a destructive process such as a medical specimen dissection, from data acquisition to interactive and immersive visualization, in order to build ground truth models. Acquisition is a two-step process, first involving a 3D laser scanner to get a 3D surface, and then a high resolution camera for capturing the texture. This acquisition process is repeated at each step of the dissection, depending on the expected accuracy and the specific objects to be studied. Thanks to fiducial markers, surfaces are registered on each others. Experts can then explore data using interaction hardware in an immersive 3D visualization. An interactive labeling tool is provided to the anatomist, in order to identify regions of interest on each acquired surface. 3D objects can then be reconstructed according to the selected surfaces. We aim to produce ground truths which for instance can be used to validate data acquired with MRI. The system is applied to the specific case of white fibers reconstruction in the human brain.