\begin{thebibliography}{1} \bibitem{WikipediaAStar2007} \_\_\_\_\_\_\_. \newblock A* search algorithm. \newblock Technical report, Wikipedia, the free encyclopedia, 2007, Available online: % \href{\url{http://en.wikipedia.org/wiki/A*_search}}% {\url{http://en.wikipedia.org/wiki/A*_search}}%. \bibitem{Andrews2007a} J.~Andrews and J.~Sethian. \newblock Fast marching methods for the continuous traveling salesman problem. \newblock {\em Proceedings of the National Academy of Sciences (PNAS)}, 104(4):1118--1123, 2007. \bibitem{Aylward2002a} S.~Aylward and E.~Bullitt. \newblock Initialization, noise, singularities, and scale in height ridge traversal for tubular object centerline extraction. \newblock {\em IEEE Transactions on Medical Imaging}, 21(2):61--75, 2002. \bibitem{Deschamps2001a} Thomas Deschamps. \newblock {\em Curve and Shape Extraction with Minimal Path and Level-Sets techniques: Applications to {3D} Medical Imaging}. \newblock {PhD} dissertation, University of Paris Dauphine, 2001, Available online: % \href{\url{http://math.lbl.gov/~deschamp/html/phdthesis.html}}% {\url{http://math.lbl.gov/~deschamp/html/phdthesis.html}}%. \bibitem{Sethian1999a} J.~Sethian. \newblock {\em Level Set Methods and Fast Marching Methods}. \newblock Cambridge Press, $2^{nd}$ edition, 1999. \bibitem{Wink2000a} O.~Wink, W.~Niessen, and M.~Viergever. \newblock Fast delineation and visualization of vessels in {3-D} angiographic images. \newblock {\em IEEE Transactions on Medical Imaging}, 19(4):337--346, 2000. \bibitem{Wink2004a} O.~Wink, W.~Niessen, and M.~Viergever. \newblock Multiscale vessel tracking. \newblock {\em IEEE Transactions on Medical Imaging}, 23(1):130--133, 2004. \end{thebibliography}