Empirical model of reflective bending moment for training simulation of needle intervention

Skilled doctors overcome lack of visual information during CT-guided needle intervention by estimating the position of the needle using haptic sensation. Simulation to train the skill using haptic sensation has been developed, and realistic haptic sensation should be rendered in real-time to enhance the effect of training simulation. In order that, a model to calculate the reflective force and moment is necessary. This paper focuses on modeling the reflective bending moment that occurs when the angle of the inserted needle changes. Experiments to measure the reflective bending moment are performed by inserting a needle into porcine tissues using a 6-DOF articulated robot. As a result, it was confirmed that the reflective bending moment is linearly proportional to the bending angle and the effect of angular velocity change is negligible. On the basis of the measurement result, the reflective bending moment is modeled as a function of insertion length, bending angle of the needle, and position that the human force is applied. The accuracy is verified by comparing the model with measurement data using porcine tissues. The proposed model can describe the reflective bending moment with less than 5.4% error for single-layer tissue and 12.5% error for multi-layer tissue. The proposed model can be applied for real-time haptic rendering of training simulation of needle intervention.