Force Modeling For Needle Insertion Into Soft Tissue And Measurement Of Needle Deflection

The paper takes the robot-assisted percutaneous surgery as the object of study.The mechanism of needle-tissue is researched extensively in this thesis. Therein, theinsertion force model and its influence factors are discussed. In addition, the needledeflection is measured based on the binocular vision technology. The force modelduring needle insertion into soft tissue is important for improving the accuracy ofpercutaneous intervention. A thorough understanding of the mechanics ofneedle-tissue interaction is necessary to optimize the needle design and roboticallyneedle steering, and surgical simulation systems.In order to build the insertion force model accurately, the interaction force isdivided into three parts: stiffness force, friction force, and cutting force. The stiffnessforce is modeled on the basis of contact mechanics model. The friction force model ispresented using a modified Winkler’s foundation model. The cutting force is viewedas a constant depending of a given tissue. The proposed models in the paper areestablished based on the mechanical properties and geometric parameters of theneedle and soft tissue. The experimental results illustrate that the proposed forcemodel is capable of predicting the needle-tissue interaction.It is obvious that the interaction is influenced by numerous variable parameters.A series of experiments have been designed and performed to explore the effect ofdifferent influence factors, while the puncture force and force density were recorded.A special tissue-mimicking phantom with similar mechanical properties andmicroscopic structures is used as a soft tissue substitute material. In addition, thedifferent tip shapes and gel interactions are observed using microscopic images.The needle deflection is caused by the force acting on the needle due to theasymmetric needle shape. In order to acquire the quantitative deflection, anexperimental setup is constructed. According to the triangular geometric principlesbinocular vision to obtain the deflection information in plane, then reconstructsthree-dimensional model of the needle. The bevel-tipped needle is viewed as acantilever beam which the force only acts on the needle tip. In finally, the deflection iscompared with different needle diameters and different needle types.