Hideo Yokota

Simulations of Needle Insertion by Using a Eulerian Hydrocode FEM and the Experimental Validations

In this paper, simulations for needle insertion were performed by using a novel Eulerian hydrocode FEM, which was adaptive for large deformation and tissue fracture. We also performed experiments for the same needle insertion with silicon rubbers and needles, which had conical tips of different angles in order to investigate the accuracy of the simulations. The resistance forces in the simulations accurately followed those in the experiments until the conical portion of the needle was inside the rubbers, and the validation of the Eulerian hydrocode was revealed. However, the present simulation showed that after the conical portion was inside the tissue, the simulated resistance forces became lower than the experimental ones. The proportional increase of the friction forces and the roughly flatness of the tip force along the time were simulated. It was predicted that the tightening force along the needle side was underestimated.

Decision algorithm for 3D blood vessel loop based on a route edit distance

This paper reports on a method to distinguish true from false of the loop in the blood vessel graph. Most conventional studies have used a graph to represent 3D blood vessels structure. Blood vessels graph sometimes has a false loop and this exerts a harmful influence to the graph analysis. Conventional study simply cut them but this is not suitable for the graph include real loop. For this reason, we try to distinguish true from false of the loop in the graph. Our method uses the loop inside and the outside main blood vessel shape to distinguish the similar loop. This main blood vessel we called route is long, thick, and not shares to other route as much as possible. Even if a graph includes false loop, this main route will avoid the false connection and detect the same main blood vessel. Our method detects such a main route in each loop branch point and stores it as the outside feature for comparing. Inside feature is measured by converting the inside blood vessels as one route. Each loop is compared by the graph edit distance. Graph edit distance is easily able to deal with the route adding, deleting and replacing. Our method was tested by the cerebral blood vessels image in MRI. Our method tried to detect the arterial cycles of Willis from the graph including false loops. As a result, our method detected it correctly in four data from five.