Pengfei Huang

Virtual Surgery Deformable Modelling Employing GPU Based Computation

The development of Virtual Environment (VE) systems is a challenging endeavor with a complex problem domain. The experience in the past decade has helped contribute significantly to various measures of software quality of the resulting VE systems. However, the resulting solutions remain monolithic in nature without addressing successfully the issue of system interoperability and software aging. This paper argues that the problem resides in the traditional system centric approach and that an alternative approach based on system of systems engineering is necessary. As a result, the paper presents a reference architecture based on layers, where only the core is required for deployment and all others are optional. The paper also presents an evaluation methodology to assess the validity of the resulting architecture, which was applied to the proposed core layer and involving individual sessions with 12 experts in developing VE systems.To achieve the real-time requirement of realistic deformable modelling, it is necessary to use the acceleration techniques such as GPU computing for FEM and employ the feasible hybrid structures in a virtual surgery simulation system. In this paper, we present a linear or nonlinear deformable model of soft tissue. In addition to the efficient meshing and basic finite element method, the high computation rate is achieved through two novel methods. Firstly, the major calculation work in the conjugate gradient solver for deformation is moved from the CPU to GPU in order to promote the calculation. Secondly, we apply the hybrid structures of deformable models, by fully calculating the volumetric deformation in the local operation part while only calculating the global deformation by medial representation method. Experiments have been given to show the feasibility and efficiency of the model.

Soft Tissue Deformation Simulation in Virtual Surgery using Nonlinear Finite Element Method

Simulation for soft tissues realistic deformation is an important part in Virtual Surgery. For large global deformation of soft tissue, linear elastic models are inappropriate, such as Mass-Spring and linear Finite Element Method (FEM). In this paper we present a simulation for 3D soft tissue using nonlinear strain computation. To get a finer mesh for FEM, we consider meshing algorithm based on Improved Delaunay criterion. Besides, we would present Spatial Hashing Collision Detection method and some improvement for real-time computation.

Hierarchical spatial hashing-based collision detection and hybrid collision response in a haptic surgery simulator

Collision detection and response are two crucial aspects in a virtual surgery simulator, which significantly affect the output in real‐time response and simulation realism.

Real-time Cutting and Suture Simulation Using Hybrid Elastic Model

In this work, our aim is to model realistic cutting and suture in real-time. For realistic rendering, the response of deformable soft tissue during the cutting and suture process should be carefully analyzed and simulated. Therefore, different behaviors of tissue resistance need to be simulated in the different phases of tool-tissue interaction. In the first phase of cutting and suture, before the tool fractures the surface we model resistance of the tissue as surface tension. Afterwards, when the tool moves into the tissue, the friction between tool and soft tissue is simulated. In addition, a hybrid elastic model consisting of a mass-spring surface with a skeleton structure is employed to speed up calculation. In our research, an abstract blood vessel is used as a case study.

A Novel Biomedical Meshing Algorithm and Evaluation based on Revised Delaunay and Space Disassembling

The tetrahedral mesh generation part in finite element method (FEM) of soft tissue simulation is difficult to be realized by traditional mesh algorithms because of the requirements of boundary preservation and quality of all tetrahedra. Aiming to meet the real-time requirement of FEM, we propose a revised Delaunay algorithm with many improved methods, including background gird, random point disarrangement, radial method and visibility check. In this paper, two tetrahedral mesh generation algorithms including Space-Disassembling and the revised Delaunay algorithm, are presented based on different mesh requirements. And a comparison of Space-Disassembling Mesh Algorithm, traditional Delaunay algorithm and the revised Delaunay algorithm is processed based on some pivotal criteria.

Image-guided surgery planning for breast reconstruction flap design

In this paper, a computer aided breast reconstruction surgery planning method is proposed, computing the breast shape after excision of one for some diseases such as cancer. In order to achieve a reasonable result, we calculate shape, area, volume and depth of the skin and muscle for the reconstruction, based on another wholesome breast. The solution is described as follows: firstly, the breasts MRI data of patient is input; then, the region of interest is obtained from healthy breast employing balloon segmentation algorithm and retrieve surface mesh data; thirdly, the dimensional surface skin mesh is mapped onto the plane, in order to attain the shape and volume of the flap for breast reconstruction, by the help of deformable model; finally the approximate curve volume shape of flap is calculated. Other contributing methods such as mesh smoothing and cutting of triangulated surface are also discussed. The doctors validation and evaluation process are also provided to ensure the robust and stable result of virtual surgery planning.

Deformation modeling using global medial representation structures and evaluation by biset mesh matching

In this paper, we present a novel hybrid deformation model using global mass-spring medial representation structures and local finite element model. We employ the hybrid models, by fully calculating the FEM deformation in the local operation part while only calculating the global deformation by medial representation method. To achieve the real-time requirement of realistic deformable modeling, it is necessary to use the GPU parallel computing for FEM on regional deformation details, so the major calculation work in the conjugate gradient solver for the solution matrix is moved from CPU to GPU to accelerate the effectiveness. Evaluation and experiments are also discussed.

New Tetrahedral Mesh Generation Method based on Delaunay Criteria and Space Disassembling

The requirement of tetrahedral mesh generation algorithm, which is a prerequisite of many soft tissue simulation methods, becomes very strict because of the real-time requirement of the simulation. Aiming to speed up the computation in the simulation, we propose a revised Delaunay algorithm which makes a good balance of quality of tetrahedra, boundary preservation and time complexity, with many improved methods. Another mesh algorithm named space-disassembling is also presented in this paper, and a comparison of space-disassembling, traditional Delaunay algorithm and the revised Delaunay algorithm is processed based on the simulation criteria.

A Hybrid Optimization Model Based on Multi-Metrics for Registration Using Free-Form Deformation

We propose a new optimization model for non-rigid registration of images using multi-metrics. The ordinary searching step of optimization has been often trapped in local minima and produces wrong registration results. In this paper, if the condition occurs, multi-metrics model will switch to the other metrics to get rid of the local minima, vice versa. We have tested our approach in a variety of experimental conditions and compared the results with the optimization without multi-metrics. The results indicate that the new model is robust and fast in non-rigid registration.

A hybrid optimization model based on multi-metrics for registration using free-form

We propose a new optimization model for non-rigid registration of images using multi-metrics. The ordinary searching step of optimization has been often trapped in local minima and produces wrong registration results. In this paper, if the condition occurs, multi-metrics model will switch to the other metrics to get rid of the local minima, vice versa. We have tested our approach in a variety of experimental conditions and compared the results with the optimization without multi-metrics. The results indicate that the new model is robust and fast in non-rigid registration.