Modeling of needle insertion forces for robot-assisted percutaneous therapy

Force information from needle insertions was measured and modeled for use in robot-assisted percutaneous therapies. Data was collected on bovine livers using the Johns Hopkins University Steady Hand Robot, and modeled in three parts: force due to capsule stiffness, friction, and cutting. Capsule stiffness is modeled by a nonlinear spring model, friction by a modified Karnopp model, and cutting by the remaining forces, which appear to be constant for a given tissue sample. During robot-assisted procedures, real-time force data can be compared to these models to control puncture of interior structures. Future work will combine imaging with force data to characterize tissue layers in specific applications, such as liver ablation and prostate brachytherapy.