“…The steering mechanisms are classified into seven different categories: base manipulation [7], duty-cycled bevel tip (with and without pre-curve) [8, 9, 10, 11], pre-curved stylet [12], active cannula [13,14], programmable bevel tip [4,15,16], tendon actuated tip [17,18] and most recently, optically controlled needle [19]. Finite element analysis [21,22], beam theory [23,24] and spring foundations [25] have all been used to derive deflection models for steerable needles. Specifically, Oldfield et al [20] considered the deflection of the programmable bevel-tip needle design, but the analysis is restricted to 2D.…”