Zou Yanni, Liu Peter X
the School of Information Engineering, Nanchang University, Jiangxi, Nanchang 330031, China.
the School of Information Engineering, Nanchang University, Jiangxi, Nanchang 330031, China; the Department of System and Computer Engineering, Carleton University, Ottawa K1S 5B6, Canada.
Comput Methods Programs Biomed. 2017 Sep;148:113-121. doi: 10.1016/j.cmpb.2017.06.013. Epub 2017 Jul 4.
In order to achieve a high degree of visual realism in surgery simulation, we propose a new model, which is based on point primitives and continuous elastic mechanics theory, for soft tissue deformation, tearing and/or cutting.
The model can be described as a two-step local high-resolution strategy. First, appropriate volumetric data are sampled and assigned with proper physical properties. Second, sparsely sampled points in non-deformed regions and densely-sampled points in the deformed zone are selected and evaluated. By using a meshless deformation model based on point primitives for all volumetric data, the affine transform matrix of collision points can be computed. The new positions of neighboring points in the collided surface can be then calculated, and more details in the local deformed zone can be obtained for rendering. Technical details about the derivations of the proposed model as well as its implementation are given.
The visual effects and computation cost of the proposed model are evaluated and compared with conventional primitives-based methods. Experimental results show that the proposed model provides users (trainees) with improved visual feedback while the computational cost is at the same magnitude of other similar methods.
The proposed method is especially suitable for the simulation of soft tissue deformation and tearing because no grid information needs to be maintained. It can simulate soft tissue deformation in a high degree of authenticity with real-time performance. It could be considered implemented in the development of a mixed reality application of neurosurgery simulators in the future.
为了在手术模拟中实现高度的视觉真实感，我们提出了一种基于点基元和连续弹性力学理论的新模型，用于软组织变形、撕裂和/或切割。
该模型可描述为一种两步局部高分辨率策略。首先，对适当的体数据进行采样并赋予适当的物理属性。其次，选择并评估未变形区域中的稀疏采样点和变形区域中的密集采样点。通过对所有体数据使用基于点基元的无网格变形模型，可以计算碰撞点的仿射变换矩阵。然后可以计算碰撞表面中相邻点的新位置，并获得局部变形区域中的更多细节以进行渲染。给出了所提出模型的推导及其实现的技术细节。
对所提出模型的视觉效果和计算成本进行了评估，并与传统的基于基元的方法进行了比较。实验结果表明，所提出的模型在计算成本与其他类似方法处于同一量级的同时，为用户（受训人员）提供了更好的视觉反馈。
所提出的方法特别适用于软组织变形和撕裂的模拟，因为无需维护网格信息。它可以以实时性能高度逼真地模拟软组织变形。未来可考虑在神经外科模拟器的混合现实应用开发中实施该方法。
