虚拟手术中缝合仿真的初步研究

初步实现了一个虚拟缝合仿真系统,可以模拟针穿刺柔性体并牵引所附缝合线穿过柔性体的过程。用户通过Phantom Desktop力反馈设备控制虚拟针的运动。柔性体在针和缝合线的作用下会发生变形。缝合线使用非均匀可变长刚性杆模型和FTL(Follow the Leader)变形算法。柔性体使用线弹性材料和Tensor-Mass变形算法。针穿刺柔性体时柔性体对针运动的阻力传给力反馈设备,而其反作用力则施加于柔性体之上。缝合线在针的牵引下穿过柔性体形成滑动约束点。缝合线的变形将在滑动约束点产生弹性力作用于柔性体之上,而柔性体的变形则反过来影响滑动约束点的位置。将约束点对应的缝合线顶点编号增加和约束点两侧刚性杆长度调整相结合,实现了缝合线光滑穿过柔性体的效果。最后给出对含有切口形状的柔性体模型进行缝合仿真的实验结果,并讨论未来的改进和发展方向。

Preliminary Study of Simulating Suture Operation in Virtual Surgery

A suture simulation system was developed.Using a Phantom desktop haptic device,user can insert a virtual needle into a deformable object and pull a virtual thread attached to the needle through the object.The object can deform under the interaction of both the needle and the thread.The thread is modeled as a series of rigid links with non-uniform variable-lengths and FTL(Follow the Leader) algorithm is used for its deformation.Tensor-mass deformation method based on linear elasticity is used for the deformable object.The resistant force acting on the needle when the needle is piercing the object is sent to the haptic device while its reaction-force is applied to object surface.Sliding constraints are formed when the thread is being pulled through the object.At each sliding constraint point,internal elastic force of the thread due to elongation is applied to the object,while the deformation of the object affects the position of the constraint point conversely.Smooth movement of the thread through sliding constraint point is achieved by combining two methods: Increment of constrained suture vertex ids and adjusting lengths of rigid links on both sides of the constraint.Suture simulation on deformable object with cutting wound was performed and the results and future improvements were discussed.