As a flexible needle with a bevel tip is pushed through soft tissue, the asymmetry of the tip causes the needle to bend. We propose that, by using nonholonomic kinematics, control, and path planning, an appropriately designed needle can be steered through tissue to reach a specified 3D target. Such steering capability could enhance targeting accuracy and may improve outcomes for percutaneous therapies, facilitate research on therapy effectiveness, and eventually enable new minimally invasive techniques. In this paper, we consider a first step toward active needle steering: design and experimental validation of a nonholonomic model for steering flexible needles with bevel tips. The model generalizes the standard three degree-of-freedom (DOF) nonholonomic unicycle and bicycle models to 6 DOF using Lie group theory. Model parameters are fit using experimental data, acquired via a robotic device designed for the specific purpose of inserting and steering a flexible needle. The experiments quantitatively validate the bevel-tip needle steering model, enabling future research in flexible needle path planning, control, and simulation.

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Nonholonomic Modeling of Needle Steering

Curve-skeletons are thinned 1D representations of 3D objects useful for many visualization tasks including virtual navigation, reduced-model formulation, visualization improvement, animation, etc. There are many algorithms in the literature describing extraction methodologies for different applications; however, it is unclear how general and robust they are. In this paper, we provide an overview of many curve-skeleton applications and compile a set of desired properties of such representations. We also give a taxonomy of methods and analyze the advantages and drawbacks of each class of algorithms.

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Curve-Skeleton Properties, Applications, and Algorithms

Individual Differences in Spatial Abilities

Nonholonomic Modeling of Needle Steering.

INTRODUCTION The Internet and worldwide web have expanded opportunities for the provision of a flexible, convenient and interactive form of continuing medical education (CME). Larger numbers of doctors are accessing and using the Internet to locate and seek medical information. It has been suggested that a significant proportion of this usage is directly related to questions that arise from patient care. A variety of Internet technologies are being used to provide both asynchronous and synchronous forms of web-based CME. Various models for designing and facilitating web-based CME learning have also been reported. The purpose of this study was to examine the nature and characteristics of the web-based CME evaluative outcomes reported in the peer-reviewed literature. METHODS A search of Medline was undertaken and the level of evaluative outcomes reported was categorised using Kirkpatrick’s model for levels of summative evaluation. RESULTS The results of this analysis revealed that the majority of evaluative research on web-based CME is based on participant satisfaction data. There was limited research demonstrating performance change in clinical practices and there were no studies reported in the literature that demonstrated that web-based CME was effective in influencing patient or health outcomes.

A review of evaluation outcomes of web-based continuing medical education.

The purpose of this study was to use a simulated virtual reality environment for training of surgical skills and then to identify if the learning that occurred was transferable to a real world surgical task. The virtual surgical tasks consisted of bimanual carrying, needle passing and mesh alignment. In this ongoing study, the experimental group (n=5) was trained by performing four iblocks of the virtual surgical tasks using the da Vinci surgical robot. Pre and post training, all subjects were tested by performing a suturing task on a "life-like" suture pad. The control group (n=5) performed only the suturing task. Significantly larger pre and post differences were revealed in time to task completion (p<0.05) and total distance travelled by the dominant side instrument tip (p<O.O l) in the experimental group as compared to the control group. These differences were specific to the suture mnning aspect of the surgical task. In conclusion, virtual reality surgical skills training may produce a significant learning effect that can transfer to actual robot-assisted laparoscopic procedures.

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Joshua Pickhinke

Papers

Medicine Meets Virtual Reality 17