Flexible Needle Bending And Spring-back Prediction And Needle Shape Reconstruction

Percutaneous insertion procedures are commonly used operations in minimally invasive surgery.Compared with using traditional straight,rigid needles,using flexible needles to conduct insertion operations can provide access to previously inaccessible target for traditional needles,avoiding vital tissues(e.g.,blood vessels and nerves),and improving targeting and safety,reducing complication rates.Thereby the steerable flexible needles have intrigued researchers exceedingly.During the flexible needle insertion,in order to lead needle achieve a target precisely,knowing the deflection of needle embedded in tissue is of importance.Regrettably,the deflection of needle in tissue can not be get directly,therefore resorting to some modalities monitoring or predicting it in real-time is of necessity.However,with the flexible needle bending,it would generate a spring-back whilst it rotates,which would lead the flexible needle deviate from its original route,increasing the risk of operation.To solve the problem mentioned above,In the Section-II,the needletissue interactive relationship during an insertion was analyzed based on mechanics,describing the forces applied on needle as the input force,the clamp force,the clamp friction,the tissue counteractive force,the tissue counteractive friction and the cutting counteractive force.The reason causing needle bending was attributed to the tissue counteractive force,the cutting counteractive force and friction,based on which a method based on the principle of minimum potential energy,Rayleigh–Ritz method,was used to model the needle bending in the space.In the Section-Ⅲ,the reason casuing needle spring-back was analyzed and was attributed to the orientation change of the three forces,based on which a model calculating the needle spring-back was developed,which was composed with the needle bending model,predicting the needle deflection in the space with considering the spring-back.In the Section-Ⅳ,the basic principle of working as well as shape reconstruction of FBG were introduced and analyzed,and a method reconstructing the needle shape based on Fiber Bragg Grating sensors(FBG).Five sets of three FBG sensors was placed along the length of the needle,and combined the feedback information sampled by FBG when it bending with the method based on Cosserat rod theory to reconstruct the 3D needle shape.In the Section-Ⅴ,In order to validate the methods above,several insertion experiments were conducted in this paper,and the cameras was used to capture the needle profile viewed as the ground truth,which was compared with the counterparts calculated by the methods propos ed in this paper.The result shows that with using the proposed methods,the needle deflection in space with considering the spring-back can be predict with 0.45mm(0.35 mm,0.98mm)mean(RMS,maximum,)errors,and the needle shape can be reconstructed with 0.15mm(0.18 mm,0.21mm)mean(RMS,maximum)errors,showing clinically acceptable accuracy.