Blood vessel modeling for interactive simulation of interventional neuroradiology procedures.

Endovascular interventions can benefit from interactive simulation in their training phase but also during pre-operative and intra-operative phases if simulation scenarios are based on patient data. A key feature in this context is the ability to extract, from patient images, models of blood vessels that impede neither the realism nor the performance of simulation. This paper addresses both the segmentation and reconstruction of the vasculature from 3D Rotational Angiography data, and adapted to simulation: An original tracking algorithm is proposed to segment the vessel tree while filtering points extracted at the vessel surface in the vicinity of each point on the centerline; then an automatic procedure is described to reconstruct each local unstructured point set as a skeleton-based implicit surface (blobby model). The output of successively applying both algorithms is a new model of vasculature as a tree of local implicit models. The segmentation algorithm is compared with Multiple Hypothesis Testing (MHT) algorithm (Friman et al., 2010) on patient data, showing its greater ability to track blood vessels. The reconstruction algorithm is evaluated on both synthetic and patient data and demonstrate its ability to fit points with a subvoxel precision. Various tests are also reported where our model is used to simulate catheter navigation in interventional neuroradiology. An excellent realism, and much lower computational costs are reported when compared to triangular mesh surface models.

Local implicit modeling of blood vessels for interactive simulation.

In the context of computer-based simulation, contact management requires an accurate, smooth, but still efficient surface model for the blood vessels. A new implicit model is proposed, consisting of a tree of local implicit surfaces generated by skeletons (blobby models). The surface is reconstructed from data points by minimizing an energy, alternating with an original blob selection and subdivision scheme. The reconstructed models are very efficient for simulation and were shown to provide a sub-voxel approximation of the vessel surface on 5 patients.

[Evolution and transformation in animal organism of some polychlorobiphenyls (author's transl)]. / Evolution et transformation dans l'organisme animal de quelques polychlorobiphényles à l'état pur. Contribution à l'étude d'un produit commercial.

Intoxication by pure polychlorobiphenyls and a commercial product is studied, in rats, after intraperitoneal and oral administration. Their fixation and excretion of their metabolites is greater by intraperitoneal than by oral administration. The only hydroxy metabolites, identified by means of synthesis, gas chromatography and mass spectrometry are, all, derivatives from trichlorobiphenyl. It appears that administration of commercial product induces a more rapid degradation of these compounds in animal organism.

[Experimental toxocologic study of some trichlorobiphenyl isomers]. / Etude toxicologique expérimentale de quelques isomères du trichlorobiphényle

The authors, after having performed the preparation of a few pure trichlorobiphenyl isomers, proceeded with a preliminary toxicological study of the rat which should then facilitate study for a commerical product. The fixation level of these compounds is considerably higher in lipids and in the spleen than in the other organs. Urinary elimination is very low compared with faecal excretion; furthermore, chromatographic analysis makes it possible to shed light on phenolic products of transformation in the excreta, some of which it was possible to identify with hydroxylated trichlorobiphenyls synthesized in the laboratory.