Surgery Simulation System Research Articles

Developing a piezoresistive sensor based bionic neurological intraoperative monitoring system for spine surgery skill training.

This research aims to tackle the limitations faced in surgical education nowadays, particularly in the complex field of spinal cord tumor removal surgery. An innovative flexible piezoresistive sensor designed to mimic a motor nerve was developed and integrated into a bionic spine surgery simulation system, allowing for the intraoperative nerve monitoring possible during simulated tumor removal surgeries. The motor nerve, fabricated using a combination of carbon nanotubes and silicone rubber, exhibited a strong correlation between applied force and resultant changes in resistance, as confirmed by experimental results. This creative system can play an important role in providing valuable feedback for training doctors, facilitating the assessment of surgical precision and success, and enabling doctors to take necessary precautions to minimize the risk of nerve damage in real surgical scenarios. Ultimately, this proposed system has the potential to elevate the standard of surgical education, foster skill development among doctors, and significantly contribute to enhanced patient care and recovery.

Haptic virtual surgery simulation system under field programmable analogue array-based hybrid control

In this paper, a bilateral haptic virtual surgery simulation system under a hybrid controller was studied. An analogue controller realized by a field programmable analogue array (FPAA) was paralleled in the operator robot side, which reduced the impact of controller discretisation on the system. A system stability conditions under hybrid control with multiple-operators were deduced. The stability analysis indicates that the addition of analogue derivative term widens the range of haptic controls gains that satisfy the multiple-users’ stability conditions. Finally, the human’s performance of a stiffness discrimination task was studied in an independently developed minimally invasive surgical (MIS) platform. The experiment results show that, human operators under the hybrid controller achieve the highest task success rates.

3D visualization and simulation in surgical planning of orbital hypertelorism

Background: simulation and three-dimensional visualization of object motion is a prerequisite for any surgical planning system. Orbital hypertelorism is a disease, which is most commonly associated with craniofacial malformations. We have developed a surgical planning system for planning and evaluation of orbital hypertelorism surgery. In our system CT-based virtual surface models fitted by oriented bounding boxes (OBB) are manipulated. Three-dimensional motion as well as a correction surgery can be simulated. Both are controlled by collision detection. The computer-based interactive surgery simulation systems (CISSS) presented here can take virtual surgical operation and forecast facial features after the correction of orbital hypertelorism.

Establishment of Emergency Teaching Model and Optimization of Discrete Dynamic Calculation in Complex Virtual Simulation Environment

Virtual surgery is a typical application of virtual reality technology in the medical field, which can help improve the success rate of surgery and reduce medical costs in various aspects such as medical training, surgery planning, and intraoperative navigation, and is becoming a hot research topic and a frontier subject in the medical field. The establishment of virtual surgery simulation system involves the intersection and penetration of various disciplines, and the research is difficult, and many functional modules are still not perfect. This study focuses on the key technologies in the virtual surgery simulation system, focusing on two core modules, the soft tissue modeling method and the collision detection algorithm, to improve the accuracy of the soft tissue model deformation under the condition of meeting the real-time system. The biomechanical properties of soft tissues are studied, the viscoelastic properties are analyzed, and the viscoelastic theory is used as the basis for soft tissue modeling; the geometric model is established by using a complementary method of surface model and tetrahedral mesh cells, with the surface model covering the outer surface for visual rendering and the tetrahedral mesh cells for skeleton support of the physical model, so that the model has a better visual effect and deformation effect, which enhances the model fidelity that is enhanced by the better visual effect and deformation effect; the soft tissue physical modeling method is summarized and summarized to lay the foundation for soft tissue model optimization. The experimental results show that the bilateral teleoperation system under analog control can give the operator a better haptic sensation (smaller value of input impedance felt by the operator when doing free motion from the robot) while ensuring good positional tracking and force tracking effects. This method solves the problems of collapse distortion and lack of viscoelastic properties of the traditional mass-spring model, and improves the accuracy of model deformation. Based on the improved algorithm, the viscoelastic hybrid filled sphere model of the liver organ is successfully established, which proves that the modeling method is feasible and effective.

The heaney transfixion stitch: a cognitive task-analysis based educational video

To teach the critical actions used to perform a Heaney transfixion pedicle ligation (“Heaney stitch”). Mapping the decisions made by experts while performing surgical skills can reveal cognitive mental representations utilized to achieve mastery performance. Cognitive task analysis (CTA) is a method used to deconstruct tasks to identify critical knowledge, action steps, and decision points that may be unintentionally automated by experts. CTA increases the accuracy and completeness of surgeons’ instructions on how to complete tasks and has been utilized for making educational interventions in general surgery, plastic surgery, and orthopedics. Three experts and three novices were interviewed on how to perform a Heaney stitch. Eighteen common critical action points were identified and used to generate an educational video. Using the Fundamentals of Vaginal Surgery (FVS) task trainer, this CTA-based educational video will instruct learners on proper needle loading; suture management; needle placement; how to optimize visualization; and efficiency of motion. This is the first of a planned series of educational videos for the Fundamentals of Vaginal Surgery (FVS) Simulation System.

A Real-time Cutting Model Based on Finite Element and Order Reduction

Telemedicine plays an important role in Corona Virus Disease 2019 (COVID-19). The virtual surgery simulation system, as a key component in telemedicine, requires to compute in real-time. Therefore, this paper proposes a real-time cutting model based on finite element and order reduction method, which improves the computational speed and ensure the real-time performance. The proposed model uses the finite element model to construct a deformation model of the virtual lung. Meanwhile, a model order reduction method combining proper orthogonal decomposition and Galerkin projection is employed to reduce the amount of deformation computation. In addition, the cutting path is formed according to the collision intersection position of the surgical instrument and the lesion area of the virtual lung. Then, the Bezier curve is adopted to draw the incision outline after the virtual lung has been cut. Finally, the simulation system is set up on the PHANTOM OMNI force haptic feedback device to realize the cutting simulation of the virtual lung. Experimental results show that the proposed model can enhance the real-time performance of telemedicine, reduce the complexity of the cutting simulation and make the incision smoother and more natural.

Design and Evaluation of Personalized Percutaneous Coronary Intervention Surgery Simulation System.

In recent years, medical simulators have been widely applied to a broad range of surgery training tasks. However, most of the existing surgery simulators can only provide limited immersive environments with a few pre-processed organ models, while ignoring the instant modeling of various personalized clinical cases, which brings substantive differences between training experiences and real surgery situations. To this end, we present a virtual reality (VR) based surgery simulation system for personalized percutaneous coronary intervention (PCI). The simulation system can directly take patient-specific clinical data as input and generate virtual 3D intervention scenarios. Specially, we introduce a fiber-based patient-specific cardiac dynamic model to simulate the nonlinear deformation among the multiple layers of the cardiac structure, which can well respect and correlate the atriums, ventricles and vessels, and thus gives rise to more effective visualization and interaction. Meanwhile, we design a tracking and haptic feedback hardware, which can enable users to manipulate physical intervention instruments and interact with virtual scenarios. We conduct quantitative analysis on deformation precision and modeling efficiency, and evaluate the simulation system based on the user studies from 16 cardiologists and 20 intervention trainees, comparing it to traditional desktop intervention simulators. The results confirm that our simulation system can provide a better user experience, and is a suitable platform for PCI surgery training and rehearsal.

Interactive hepatic parenchymal transection simulation with haptic feedback

BackgroundLiver resection involves surgical removal of a portion of the liver. It is used to treat liver tumors and liver injuries. The complexity and high-risk nature of this surgery prevents novice doctors from practicing it on real patients. Virtual surgery simulation was developed to simulate surgical procedures to enable medical professionals to be trained without requiring a patient, a cadaver, or an animal. Therefore, there is a strong need for the development of a liver resection surgery simulation system. We propose a real-time simulation system that provides realistic visual and tactile feedback for hepatic parenchymal transection. MethodsThe tetrahedron structure and cluster-based shape matching are used for physical model construction, topology update of a three-dimensional liver model soft deformation simulation, and haptic rendering acceleration. During the liver parenchyma separation simulation, a tetrahedral mesh is used for surface triangle subdivision and surface generation of the surgical wound. The shape-matching cluster is separated via component detection on an undirected graph constructed using the tetrahedral mesh. ResultsIn our system, cluster-based shape matching is implemented on a GPU, whereas haptic rendering and topology updates are implemented on a CPU. Experimental results show that haptic rendering can be performed at a high frequency (>900Hz), whereas mesh skinning and graphics rendering can be performed at 45fps. The topology update can be executed at an interactive rate (>10Hz) on a single CPU thread. ConclusionsWe propose an interactive hepatic parenchymal transection simulation method based on a tetrahedral structure. The tetrahedral mesh simultaneously supports physical model construction, topology update, and haptic rendering acceleration.

The Fundamentals of Vaginal Surgery pilot study: developing, validating, and setting proficiency scores for a vaginal surgical skills simulation system

Surgical training in the simulation lab can develop basic skills that translate to the operating room. Standardized, basic skills programs that are supported by validated assessment measures exist for open, laparoscopic, and endoscopic surgery; however, there is yet to be a nationally recognized and widely implemented basic skills program specifically for vaginal surgery. Develop a vaginal surgical simulation system; evaluate robust validity evidence for the simulation system and its related performance measures; and establish a proficiency score that discriminates between novice and experienced vaginal surgeon performance. In this 3-phased study, we developed the Fundamentals of Vaginal Surgery simulation system consisting of (1) the Fundamentals of Vaginal Surgery Trainer, a task trainer; (2) a validated regimen of tasks to be performed on the trainer; and (3) performance measures to determine proficiency. In Phase I, we developed the task trainer and selected surgical tasks by performing a needs assessment and hierarchical task analyses, with review and consensus from an expert panel. In Phase II, we conducted a national survey of vaginal surgeons to collect validity evidence regarding test content, response process, and internal structure relevant to the simulation system. In Phase III, we compared performance of novice (first and second year residents) and experienced (third and fourth year residents, fellows, and faculty) surgeons on the simulation system to evaluate relevant relationships to other variables and consequences. Performance measures were analyzed to set a proficiency score that would discriminate between novice and expert (faculty) vaginal surgical performance. A novel task trainer and 6 basic vaginal surgical skills were developed in Phase I. In Phase II, the survey responses of 48 participants (27 faculty surgeons, 6 fellows, and 14 residents) were evaluated on the dimensions of test content, response process, and internal structure. To support evidence of test content, the participants deemed the task trainer and surgical tasks representative of intended surgical field and supportive of typical surgical actions (mean scores, 3.8-4.4/5). For response process, rater-data analysis revealed high rating variability regarding prototype color. This early evidence confirmed the value of a white prototype. For internal structure, there was high agreement among rater groups (obstetricians and gynecologists generalists vs Female Pelvic Medicine and Reconstructive Surgery specialists: interclass correlation coefficient range, 0.59-0.91; learners vs faculty interclass correlation coefficient range, 0.64-1.0). There were no differences in ratings across institution type, surgeon volume, expertise (P>.14). In Phase III, we analyzed performance from 23 participants (15 [65%] obstetricians and gynecologists residents, 3 [13%] fellows, and 5 [22%] Female Pelvic Medicine and Reconstructive Surgery faculty). Experienced surgeons scored significantly higher than novice surgeons (median, 467.5; interquartile range, [402.5-542.5] vs median, 261.5; interquartile range, [211.5-351.0]; P<.001). Based on these data, setting a proficiency score threshold at 400 results in 0% (0/6) novices attaining the score, with 100% (5/5) experts exceeding it. We present validity evidence relevant to all 5 sources which supports the use of this novel simulation system for basic vaginal surgical skills. To complement the system, a proficiency score of 400 was established to discriminate between novices and experts.

Application of Ultrasound Virtual Reality in the Diagnosis and Treatment of Cardiovascular Diseases.

Cardiovascular disease is a common chronic disease in the medical field, which has a great impact on the health of Chinese residents (especially the elderly). At present, the effectiveness of the prevention and treatment of cardiovascular diseases in my country is not optimistic. Overall, the prevalence and mortality of CVD are still on the rise. The timely and effective detection and treatment of cardiovascular and cerebrovascular diseases are of great practical significance to improve the health of residents and to carry out prevention and treatment. This article aims to study the application of ultrasound-based virtual reality technology in the diagnosis and treatment of cardiovascular diseases to improve the efficiency and accuracy of the diagnosis of cardiovascular and cerebrovascular diseases by medical staff. The focus is on the application of feature attribute selection related algorithms and classification related algorithms in medical and health diagnosis systems, and a cardiovascular and cerebrovascular disease diagnosis system based on naive Bayes algorithm and improved genetic algorithm is designed and developed. The system builds a diagnostic model for cardiovascular and cerebrovascular diseases and diagnoses and displays the corresponding results based on the patient's examination data. This paper first puts forward the theoretical concepts of ultrasonic virtual reality technology, scientific computing visualization, genetic algorithm, naive Bayes algorithm, and surgery simulation system and describes them in detail. Then, we construct a three-dimensional ultrasonic virtual measurement system, from the collection and reconstruction of image data to the filtering and segmentation of image data, plus the application of three-dimensional visualization and virtual reality technology to construct a three-dimensional measurement system. The experimental results in this paper show that 10 isolated congenital heart disease models with atrial septal defect (ASD) established through the use of three-dimensional visualization and virtual reality technology measured the short diameter, long diameter, and area of the atrial septal defect in the left and right atria. Finally, a value of L less than 0.05 indicates that the statistics are meaningful, and a value of r generally greater than 0.9 indicates that the virtual measurement result is highly correlated with the real measurement result.

VR/AR Technology in Human Anatomy Teaching and Operation Training.

AR/VR technology can fuse the clinical imaging data and information to build an anatomical environment combining virtual and real, which is helpful to improve the interest of teaching and the learning initiative of medical students, and then improve the effect of clinical teaching. This paper studies the application and learning effect of the VR/AR system in human anatomy surgery teaching. This paper first shows the learning environment and platform of the VR/AR system, then explains the interface and operation of the system, and evaluates the teaching situation. This paper takes the VR/AR operation simulation system of an Irish company as an example and evaluates the learning effect of 41 students in our hospital. Research shows that the introduction of the feature reweighting module in the VR/AR surgery simulation system improves the accuracy of bone structure segmentation (IOU value increases from 79.62% to 83.56%). For real human ultrasound image data, the IOU value increases from 80.21% to 82.23% after the feature reweighting module is introduced. Therefore, the dense convolution module and feature reweighting module improve the learning ability of the network for bone structure features in ultrasound images from two aspects of feature connection and importance understanding and effectively improve the performance of bone structure segmentation.

A study of real-time simulation of liver of virtual surgical robot based on biologically position-based dynamic model

Virtual surgery robot can accurately modeling of surgical instruments and human organs, and realistic simulation of various surgical phenomena such as deformation of organic tissues, surgery simulation system can provide operators with reusable virtual training and simulation environment. To meet the requirement of virtual surgery robot for the authenticity and real-time of soft tissue deformation and surgical simulation in liver surgery, a new method is proposed to simulate the deformation of soft tissue. This method combines the spring force, the external force of the system, and the constraint force produced by the constraint function of the position-based dynamics. Based on the position-based dynamics, an improved three-parameter mass-spring model is added. In the calculation of the elastic force, the nonlinearity and viscoelasticity of the soft tissue are introduced, and the joint force of the constraint projection process and the constraint force of the position-based dynamics is used to modify mass points movement. The method of position-based dynamics based on biological characteristics, not only considers the biomechanical properties of biological soft tissue as an organic polymer such as viscoelasticity, nonlinearity, and incompressibility but also retains the rapidity and stability of the position based dynamic method. Through the simulation data, the optimal side length of tetrahedral mesh in the improved three-parameter model is obtained, and the physical properties of the model are proved. The real-time simulation of the liver and other organs is completed by using the Geomagic touch force feedback device, which proves the practicability and effectiveness of this method.

Deformation modeling based on mechanical properties of liver tissue for virtuanormal vectors of trianglesl surgical simulation.

In this paper, a method for rapidly constructing a virtual surgical simulation system is proposed. A deformation model based on the mechanical properties of the liver and a rapid collision detection between the surgical micro-instruments and the liver tissue are included in this method. The purpose of this work is to improve the accuracy and real time of particle model deformation interaction in virtual surgery system. Firstly, a finite element model is established based on the constitutive model parameters of liver tissue. According to the simulation results, a mathematical model of node displacement is established. Secondly, the virtual liver is established based on the fast model reconstruction method, and the virtual manipulator is controlled by Geomagic Touch manipulator. Based on the hybrid bounding box, a rapid collision detection process between the instrument and liver is realized and the proposed deformation method is used to simulate the deformation of liver tissue. The simulation and experiment results show that the proposed deformation model can achieve high deformation interaction accuracy. The collision detection algorithm based on the hybrid bounding boxes can realize the collision between the liver and the instrument, and the established virtual surgical simulation system can simulate the liver tissue deformation in the case of small loading displacement. The effectiveness of the collision detection algorithm and deformation model was verified by an established virtual surgery simulation system. The proposed rapid construction method of virtual surgical simulation is feasible.

A morphing-Based 3D point cloud reconstruction framework for medical image processing

Background and Objective: In the virtual surgery simulation system, the reconstruction of a highly precise soft tissue 3D model is an effective method to improve the user’s visual telepresence. However, the traditional point cloud generation method based on subdivision and filling is unsatisfactory due to its low accuracy and slow speed.Methods: To address this problem, we present a novel 3D point cloud reconstructing model based on Morphing. The 3D surface model of soft tissue (live) is obtained from a series of 2D CT images using Mimics. The 3D voxel model of soft tissue is reconstructed through a sequential change of the 3D surface model by utilizing Morphing. A nonlinear interpolation method is used to fit the irregular shape of the model and improve simulation accuracy.Results: The point cloud model builds from discrete points, avoiding the problems of instability and computational complexity, which are inherent in both the surface and volume models for soft tissue. Compared with the volumetric subdividing and voxel filling method, the simulation results show that the 3D cloud model reconstructed based on Morphing is more fast, accurate and consistent with the real soft tissue.Conclusions: The simulating experiment of soft tissue deformation using 3D point cloud model which reconstructed using moprhing proved our method is effective and correct.

EMIG Simulation Systems Construct Validation Trial: Hysteroscopic Component

<h3>Study Objective</h3> Construct validation of the EMIG Hysteroscopic Surgery Simulation System. <h3>Design</h3> A prospective, controlled cohort comparison. <h3>Setting</h3> Thirteen teaching institutions in the US and Canada and an AAGL Congress. <h3>Patients or Participants</h3> 240 subjects who fit one of 4 categories of exposure to hysteroscopic surgery and surgical simulation: 76 novices within 100 days of starting posgraduate year 1 (PGY-1); 69 within the first 100 days of starting PGY-3; 27 American Board of Obstetrics and Gynecology (ABOG) certified and no additional fellowship training ("Proficient"); 43 who had completed the two-year Fellowship in Minimally Invasive Gynecologic Surgery (FMIGS). <h3>Interventions</h3> Subjects were oriented to the simulation system and then tested under proctor supervision on the 2 EMIG hysteroscopic exercises. These included the Targeting Exercise (H-1); and the Polyp Removal Exercise (H-2). Time and accuracy scoring were entered electronically on site, but sessions were video recorded and stored for subsequent review to optimize data quality. <h3>Measurements and Main Results</h3> Each exercise was timed, and a number of objective metrics recorded that were designed to assess accuracy, efficiency and technique. Each exercise had a "time cap"; if a subject had not completed the exercise in by the end of the alloted time, they were categorized as "Did Not Complete" and the maximum time was entered for data analysis. Preliminary data analysis demonstrates that for both H-1 and H-2 the novice group consistently demonstrated the poorest performance and the FMIGS cohort consistently the best. The PGY-3 and "Proficient" cohorts were generally similar to each other but each performed better than the PGY-1 group and well below the FMIGS group. <h3>Conclusion</h3> The EMIG Hystroscopic Simulation System can be used to distinguish amongst PGY-1, PGY-3, Proficient and FMIGS subjects. FMIGS-trained subjects consistently had the best results.

EMIG Simulation Systems Construct Validation Trial: Laparoscopic Component

Study Objective Construct validation of the EMIG Laparoscopic Surgery Simulation System. Design A prospective, controlled cohort comparison. Setting Thirteen teaching institutions in the US and Canada and an AAGL Congress Patients or Participants 221 subjects who fit one of 4 categories of exposure to laparoscopic surgery and surgical simulation: 77 novices within 100 days of starting posgraduate year 1 (PGY-1); 71 within the first 100 days of starting PGY-3; 30 American Board of Obstetrics and Gynecology (ABOG) certified and no additional fellowship training (“Proficient”); 43 who had completed the two-year Fellowship in Minimally Invasive Gynecologic Surgery (FMIGS). Interventions Subjects were oriented to the simulation system and then tested under proctor supervision on the 5 EMIG laparoscopic exercises. These included the sleeve to peg transfer (L-1); the circular pattern cut (L-2); extracorporeal knotting (L-3); intracorporeal knotting (L-4); and a running suture (L-5). Time and accuracy scoring were entered electronically on site, but sessions were video recorded and study materials such as cutting and suturing targets were labeled and stored for subsequent review to optimize data quality. Measurements and Main Results Each exercise was timed, and a number of objective metrics recorded that reflected cutting and suturing accuracy and technique. Each exercise had a “time cap”; if a subject had not completed the exercise by the end of the allotted time, they were categorized “Did Not Complete” and the maximum time was entered for data analysis. Preliminary data analysis demonstrates that the novice group consistently demonstrated the poorest performance and the FMIGS cohort consistently the best. The PGY-3 and “Proficient” cohorts were generally similar to each other but each performed better than the PGY-1 group and well below the FMIGS group. Conclusion The EMIG Laparoscopic Simulation System can be used to distinguish amongst PGY-1, PGY-3, Proficient and FMIGS subjects. FMIGS-trained subjects consistently had the best results with almost no “Did not Complete” outcomes. Construct validation of the EMIG Laparoscopic Surgery Simulation System. A prospective, controlled cohort comparison. Thirteen teaching institutions in the US and Canada and an AAGL Congress 221 subjects who fit one of 4 categories of exposure to laparoscopic surgery and surgical simulation: 77 novices within 100 days of starting posgraduate year 1 (PGY-1); 71 within the first 100 days of starting PGY-3; 30 American Board of Obstetrics and Gynecology (ABOG) certified and no additional fellowship training (“Proficient”); 43 who had completed the two-year Fellowship in Minimally Invasive Gynecologic Surgery (FMIGS). Subjects were oriented to the simulation system and then tested under proctor supervision on the 5 EMIG laparoscopic exercises. These included the sleeve to peg transfer (L-1); the circular pattern cut (L-2); extracorporeal knotting (L-3); intracorporeal knotting (L-4); and a running suture (L-5). Time and accuracy scoring were entered electronically on site, but sessions were video recorded and study materials such as cutting and suturing targets were labeled and stored for subsequent review to optimize data quality. Each exercise was timed, and a number of objective metrics recorded that reflected cutting and suturing accuracy and technique. Each exercise had a “time cap”; if a subject had not completed the exercise by the end of the allotted time, they were categorized “Did Not Complete” and the maximum time was entered for data analysis. Preliminary data analysis demonstrates that the novice group consistently demonstrated the poorest performance and the FMIGS cohort consistently the best. The PGY-3 and “Proficient” cohorts were generally similar to each other but each performed better than the PGY-1 group and well below the FMIGS group. The EMIG Laparoscopic Simulation System can be used to distinguish amongst PGY-1, PGY-3, Proficient and FMIGS subjects. FMIGS-trained subjects consistently had the best results with almost no “Did not Complete” outcomes.

Hybrid 4D cardiovascular modeling based on patient-specific clinical images for real-time PCI surgery simulation

In this paper, we proposed a hybrid 4D cardiovascular modeling method based on the clinical CTA and MRI to simulate the motion of the heart, as well as the patient-specific vessel structure attached to the heart model, in order to support the personalized Percutaneous Coronary Intervention (PCI) simulation which is used to train surgeons of skills and to help planning surgery. To obtain patient-specific vessel structure, a coarse segmentation with the centerlines extraction subsequently is applied to the computed tomography (CT) scans and the vessels along the centerlines is modeled using a lofted 2D segmentation method. The vessels are then combined with a template heart model to construct a cardiovascular system. For the cardiac motion, we estimate the ventricles motion from 4D Magnetic Resonance Imaging (MRI) sequences to drive the whole heart motion. And the position-based method coupling with a mass-spring model constructed with elastic spheres is used to simulate the cardiac motion cycle stably in the interactive PCI simulator. With our method, a personalized highly realistic beating motion of a whole heart is able to be created and applied to our patient-specific PCI surgery simulation system.

A Constitutive Model of Soft Tissue Deformation for Virtual Surgical Simulation: A Literature Review

Realistic modeling of soft tissue deformation has been recognized as an essential requirement for virtual surgical simulators. As a consequence, the constitutive model is crucial for modeling soft tissue deformation. In this paper, the significance and characteristics of soft tissue deformation in virtual surgery simulation studies are introduced and analyzed its challenges. We have been focusing on investigating the constitutive relations in the soft tissue mechanical models: viscoelastic models and hyper-elastic models. Moreover, some techniques are given to determine and optimize model parameters through biomechanical experiments. Finally, based on the existing constitutive model, a novel notion for optimizing the soft tissue deformation constitutive model is proposed. The contribution of this paper is to provide theoretical guidance for the simulation of soft tissue deformation in the virtual surgery simulation system and to supply various practical suggestions for developing new constitutive models in the future.

A Novel Haptic Interactive Approach to Simulation of Surgery Cutting Based on Mesh and Meshless Models.

In the present work, the majority of implemented virtual surgery simulation systems have been based on either a mesh or meshless strategy with regard to soft tissue modelling. To take full advantage of the mesh and meshless models, a novel coupled soft tissue cutting model is proposed. Specifically, the reconstructed virtual soft tissue consists of two essential components. One is associated with surface mesh that is convenient for surface rendering and the other with internal meshless point elements that is used to calculate the force feedback during cutting. To combine two components in a seamless way, virtual points are introduced. During the simulation of cutting, the Bezier curve is used to characterize smooth and vivid incision on the surface mesh. At the same time, the deformation of internal soft tissue caused by cutting operation can be treated as displacements of the internal point elements. Furthermore, we discussed and proved the stability and convergence of the proposed approach theoretically. The real biomechanical tests verified the validity of the introduced model. And the simulation experiments show that the proposed approach offers high computational efficiency and good visual effect, enabling cutting of soft tissue with high stability.

An efficient rotational matrix extraction scheme for finite element method-based deformation

With the development of computer science and mechanical engineering, advanced and stable soft tissue deformation modelling methods have been employed, such as mass-spring model, finite element method and meshless method. The co-rotational finite element method (co-rotational FEM), which was first introduced in physics-based computer animations, has shown its strengths to be a feasible approach to modelling the process of soft tissue deformation in a virtual surgery simulation system. In this study, we mainly investigated the method of extracting the rotational matrix which is used to perform stiffness warping assembly at each simulation time step. We first introduced and compared the time-consuming polar decomposition method and the efficient QR decomposition method, and then our hybrid rotational matrix extraction method is described. The final experimental results show that our efficient rotational matrix extraction method can improve the computation efficiency greatly without deformation accuracy losing.