Misra S, Reed K B, Schafer B W, Ramesh K T, Okamura A M
University of Twente, Enschede, The Netherlands.
Int J Rob Res. 2010 Nov;29(13):1640-1660. doi: 10.1177/0278364910369714.
The tip asymmetry of a bevel-tip needle results in the needle naturally bending when it is inserted into soft tissue. This enables robotic needle steering, which can be used in medical procedures to reach subsurface targets inaccessible by straight-line trajectories. However, accurate path planning and control of needle steering requires models of needle-tissue interaction. Previous kinematic models required empirical observations of each needle and tissue combination in order to fit model parameters. This study describes a mechanics-based model of robotic needle steering, which can be used to predict needle behavior and optimize system design based on fundamental mechanical and geometrical properties of the needle and tissue. We first present an analytical model for the loads developed at the tip, based on the geometry of the bevel edge and material properties of soft-tissue simulants (gels). We then present a mechanics-based model that calculates the deflection of a bevel-tipped needle inserted through a soft elastic medium. The model design is guided by microscopic observations of needle-gel interactions. The energy-based formulation incorporates tissue-specific parameters, and the geometry and material properties of the needle. Simulation results follow similar trends (deflection and radius of curvature) to those observed in experimental studies of robotic needle insertion.
斜面尖端针的尖端不对称性会导致针在插入软组织时自然弯曲。这实现了机器人针转向，可用于医疗程序中以到达直线轨迹无法触及的皮下目标。然而，针转向的精确路径规划和控制需要针 - 组织相互作用模型。先前的运动学模型需要对每种针和组织组合进行实证观察，以便拟合模型参数。本研究描述了一种基于力学的机器人针转向模型，该模型可用于根据针和组织的基本力学和几何特性预测针的行为并优化系统设计。我们首先基于斜面边缘的几何形状和软组织模拟物（凝胶）的材料特性，给出尖端处产生的载荷的解析模型。然后我们给出一个基于力学的模型，该模型计算插入软弹性介质中的斜面尖端针的挠度。该模型设计以针 - 凝胶相互作用的微观观察为指导。基于能量的公式纳入了组织特定参数以及针的几何形状和材料特性。模拟结果呈现出与机器人针插入实验研究中观察到的结果相似的趋势（挠度和曲率半径）。
