Soft Tissue Deformation Modeling in the Procedure of Needle Insertion:A Kriging‑Based Method

The simulation and planning system(SPS)requires accurate and real-time feedback regarding the deformation of soft tissues during the needle insertion procedure.Traditional mechanical-based models such as the finite element method(FEM)are widely used to compute the deformations of soft tissue.However,it is difficult for the FEM or other methods to find a balance between an acceptable image fidelity and real-time deformation feedback due to their complex material properties,geometries and interaction mechanisms.In this paper,a Kriging-based method is applied to model the soft tissue deformation to strike a balance between the accuracy and efficiency of deformation feedback.Four combinations of regression and correlation functions are compared regarding their ability to predict the maximum deformations of ten characteristic markers at a fixed insertion depth.The results suggest that a first order regression function with Gaussian correlation functions can best fit the results of the ground truth.The functional response of the Kriging-based method is utilized to model the dynamic deformations of markers at a series of needle insertion depths.The feasibility of the method is verified by investigating the adaptation to step variations.Compared with the ground truth of the finite element(FE)results,the maximum residual is less than 0.92 mm in the Y direction and 0.31 mm in the X direction.The results suggest that the Kriging metamodel provides real-time deformation feedback for a target and an obstacle to a SPS.

Method with repeated extraction-insertion cycles to im prove the needle insertion accuracy

In order to improve the effectiveness of percutaneous diagnosis and therapies, the needle insertion into the deforming soft and inhomogenous tissue should be accurate. In this study a needle with 6 degrees of freedom force/torque sensor is used to find the relationship between the pathway＇s length and the force. Our experiments show that the method with repeated extraction-insertion cy- cles can make the needle approach the target as much as possible. Meanwhile a method to obtain the appropriaterepeated extraction-insertion cycles is given to drive the needle to execute the repeat- ed cycles efficiently. Experiments and discussions were conducted to preliminarily validate the meth- od.

A facial reconstruction method based on new mesh deformation techniques

This article presents a new numerical method for facial reconstruction.The problem is the following:given a dry skull,reconstruct a virtual face that would help in the identification of the subject.The approach combines classical features as the use of a skulls/faces database and more original aspects:(1)an original shape matching method is used to link the unknown skull to the database templates;(2)the final face is seen as an elastic 3D mask that is deformed and adapted onto the unknown skull.In this method,the skull is considered as a whole surface and not restricted to some anatomical landmarks,allowing a dense description of the skull/face relationship.Also,the approach is fully automated.Various results are presented to show its efficiency.

Cranio-maxillofacial surgery simulation based on pre-specified target face configurations

This paper presents a novel method for assisting surgeons in automatically computing an optimal surgical plan by directly specifying the desired correction to a facial outline. First, the desired facial appearance is designed using a 3D sculpturing tool, while the cut regions of the skull are defined based on facial anatomy. Then, the deformation of the face meshes is performed using an improved biomechanical model in which virtual external forces are driven by the displacements corresponding to the differences of node coordinates between the original and specified face meshes, and free nodes and fixed nodes are defined in terms of the contact surfaces between the soft tissues and the bones within the cut regions. Finally, the shape of the contact surfaces is updated following the deformation of the soft tissues. After registering the deformable contact surfaces and the cut surfaces, the final positions of the cut bones are estimated. Evaluation of preliminary experimental results quantitatively shows the effectiveness of the proposed approach.