A Generalized Analytical Model of the Cutting Angles of a Biopsy Needle Tip

A general analytical model of the geometry of a biopsy needle tip is formulated. The model is then used to derive the correlations for the characteristic cutting mechanics angles and for their respective distribution along the active cutting edges of the needle tip. The angles are defined in analogy to the definitions used in cutting tool design for material removal operations. Specifically, analytical expressions for the inclination and rake angles of the tip are derived. The validity of the models was confirmed through their application to plausible needle tip geometries such as: flat, cylindrical and helical tips. The knowledge of the tip geometry and of the relevant angles is a prerequisite for the understanding of tissue cutting mechanics.