Modeling of friction force based on relative velocity between liver tissue and needle for needle insertion simulation.

Needle insertion treatments require accurate placement of the needle tip into the target cancer. However, it is difficult to insert the needle into the cancer because of cancer displacement due to the organ deformation. Then, a path planning using needle insertion simulation to analyze the deformation of the organ is important for the accurate needle insertion. A frictional model for needle insertion simulation is presented in this report. In particular, we focus on a model of frictional force based on the relative velocity between the needle and liver tissue ranging from hyper slow velocity. First, in vitro experiments using hog liver were performed at several relative velocities in order to measure the velocity dependence of the frictional force. Several needle insertion experiments were performed under identical conditions in order to deal with the variance of experimental data. The 60 frictional force data were used to obtain average data at each relative velocity. Second, the model of frictional force was developed using the averages of the experimental results. This model is defined according to the relative velocity ranging from hyper slow velocity. Finally, an evaluation experiment was carried out. The data obtained by the evaluation experiment reveals that the frictional force changes according to the relative velocity between the needle and liver tissue. The experimental results support the validity of proposed model of frictional force.