Design Choices in Needle Steering—A Review

Alignment errors can arise during needle tip placement in deep-seated tissue structures. This can lead to undesired diagnostic and therapeutic outcomes. Path correction by means of needle steering has been investigated in scientific studies for the past decades. Several approaches exist, each of them with their own strengths and weaknesses. This paper describes the various needle-steering techniques, and discusses their applicability in terms of mechanical design choices in order to assess and guide on-going work in this research area. Included steering techniques apply needle base manipulations, bevel tips, precurved stylets, active cannulas, programmable bevels, and tendon actuated tips. Techniques are classified as either passive or active, based on how steering is achieved. Mechanical properties of developed needles differ largely. Flexural rigidity, for instance, was found to vary with a factor 10⁶. Mechanical interactions, such as torsion and buckling, are described individually. Different research objectives have led to different steerable needle designs. Design criteria are typically based on these objectives, and not necessarily on clinical needs. However, the effectiveness of steering techniques depends heavily on this design, the navigation medium, and the intended task. In the proposed classification scheme, this dependence is quantified by the flexural rigidity.