Frictional force modeling ranging from hyper to slow relative velocity between a needle and liver tissue

Needle insertion treatments require accurate placement of a needle tip into the target cancer. However, it is difficult to insert the needle into a lesion because of tumor displacement during organ deformation. Therefore, path planning using a needle insertion simulation to analyze deformation of an organ is important for 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 a needle and liver tissue ranging from hyper to slow velocity. In vitro experiments using porcine liver were performed at several relative velocities to measure the velocity dependence of the frictional force. Sixty trials of frictional force data were used to obtain average data at each relative velocity. The model of frictional force was then developed using the averages of the experimental results. This model was defined according to relative velocity, including hyper-slow velocity. Our modeling and experimental results show that the frictional force between the tissue and the needle increased during low relative velocity (under 1.5mm/s) and became constant (over 1.5mm/s).