Personalized cardiovascular intervention simulation system

Background This study proposes a series of geometry and physics modeling methods for personalized cardiovascular intervention procedures,which can be applied to a virtual endovascular simulator.Methods Based on personalized clinical computed tomography angiography(CTA)data,mesh models of the cardiovascular system were constructed semi-automatically.By coupling 4 D magnetic resonance imaging(MRI)sequences corresponding to a complete cardiac cycle with related physics models,a hybrid kinetic model of the cardiovascular system was built to drive kinematics and dynamics simulation.On that basis,the surgical procedures related to intervention instruments were simulated using specially-designed physics models.These models can be solved in real-time;therefore,the complex interactions between blood vessels and instruments can be well simulated.Additionally,X-ray imaging simulation algorithms and realistic rendering algorithms for virtual intervention scenes are also proposed.In particular,instrument tracking hardware with haptic feedback was developed to serve as the interaction interface of real instruments and the virtual intervention system.Finally,a personalized cardiovascular intervention simulation system was developed by integrating the techniques mentioned above.Results This system supported instant modeling and simulation of personalized clinical data and significantly improved the visual and haptic immersions of vascular intervention simulation.Conclusions It can be used in teaching basic cardiology and effectively satisfying the demands of intervention training,personalized intervention planning,and rehearsing.

Orthodontic simulation system with force feedback for training complete bracket placement procedures

Background A virtual system that simulates the complete process of orthodontic bracket placement can be used for pre-clinical skill training to help students gain confidence by performing the required tasks on a virtual patient.Methods The hardware for the virtual simulation system is built using two force feedback devices to support bi-manual force feedback operation.A 3D mouse is used to adjust the position of the virtual patient.A multi-threaded computational methodology is adopted to satisfy the requirements of the frame rate.The computation threads mainly consist of the haptic thread running at a frequency of>1000Hz and the graphic thread at>30Hz.The graphic thread allows the graphics engine to effectively display the visual effects of biofilm removal and acid erosion through texture mapping.Using the haptic thread,the physics engine adopts the hierarchy octree collision-detection algorithm to simulate the multi-point and multi-region interaction between the tools and the virtual environment.Its high efficiency guarantees that the time cost can be controlled within 1 ms.The physics engine also performs collision detection between the tools and particles,making it possible to simulate paint and removal of colloids.The surface-contact constraints are defined in the system;this ensures that the bracket will not divorce from or embed into the tooth during the adjustment of the bracket.Therefore,the simulated adjustment is more realistic and natural.Results A virtual system to simulate the complete process of orthodontic bracket bonding was developed.In addition to bracket bonding and adjustment,the system simulates the necessary auxiliary steps such as smearing,acid etching,and washing.Furthermore,the system supports personalized case training.Conclusions The system provides a new method for students to practice orthodontic skills.

Augmented reality-based visual-haptic modeling for thoracoscopic surgery training systems

Background Compared with traditional thoracotomy,video-assisted thoracoscopic surgery(VATS)has less minor trauma,faster recovery,higher patient compliance,but higher requirements for surgeons.Virtual surgery training simulation systems are important and have been widely used in Europe and America.Augmented reality(AR)in surgical training simulation systems significantly improve the training effect of virtual surgical training,although AR technology is still in its initial stage.Mixed reality has gained increased attention in technology-driven modern medicine but has yet to be used in everyday practice.Methods This study proposed an immersive AR lobectomy within a thoracoscope surgery training system,using visual and haptic modeling to study the potential benefits of this critical technology.The content included immersive AR visual rendering,based on the cluster-based extended position-based dynamics algorithm of soft tissue physical modeling.Furthermore,we designed an AR haptic rendering systems,whose model architecture consisted of multi-touch interaction points,including kinesthetic and pressure-sensitive points.Finally,based on the above theoretical research,we developed an AR interactive VATS surgical training platform.Results Twenty-four volunteers were recruited from the First People's Hospital of Yunnan Province to evaluate the VATS training system.Face,content,and construct validation methods were used to assess the tactile sense,visual sense,scene authenticity,and simulator performance.Conclusions The results of our construction validation demonstrate that the simulator is useful in improving novice and surgical skills that can be retained after a certain period of time.The video-assisted thoracoscopic system based on AR developed in this study is effective and can be used as a training device to assist in the development of thoracoscopic skills for novices.

Interactive hepatic parenchymal transection simulation with haptic feedback

Background Liver 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.Methods The 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.Results In 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.Conclusions We 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.

Virtual reality and augmented reality in medical simulation

Virtual reality/augmented reality(VR/AR)technologies have been widely used in medical fields,such as surgical simulation,healthcare,surgical navigation,computer assisted diagnosis,medical visualization and translational medicine.In this special issue,we include 6 research papers on the application of VR/AR to medical simulation,which can be divided into two sets,including surgical simulation and medical modelling/analysis.

Dynamic ocean inverse modeling based on differentiable rendering

Learning and inferring underlying motion patterns of captured 2D scenes and then re-creating dynamic evolution consistent with the real-world natural phenomena have high appeal for graphics and animation.To bridge the technical gap between virtual and real environments,we focus on the inverse modeling and reconstruction of visually consistent and property-verifiable oceans,taking advantage of deep learning and differentiable physics to learn geometry and constitute waves in a self-supervised manner.First,we infer hierarchical geometry using two networks,which are optimized via the differentiable renderer.We extract wave components from the sequence of inferred geometry through a network equipped with a differentiable ocean model.Then,ocean dynamics can be evolved using the reconstructed wave components.Through extensive experiments,we verify that our new method yields satisfactory results for both geometry reconstruction and wave estimation.Moreover,the new framework has the inverse modeling potential to facilitate a host of graphics applications,such as the rapid production of physically accurate scene animation and editing guided by real ocean scenes.

High-temperature oxidation behavior of modified 4Al alumina-forming austenitic steel: Effect of cold rolling

The oxidation behavior and mechanism of as-received and 30 % cold-rolled alumina-forming austenitic(AFA) steel were investigated in dry air at 700℃.The results show that the mass gain per unit area curves of as-received and 30 % cold-rolled steels subject to near-parabolic law before 100 h oxidation time.Two samples both show higher high-temperature oxidation resistance due to the formation of dense Al_(2)O_(3) oxide scale.Gradual spallation of outer scale results in the formation of continuous and dense alumina scale.Dislocations can act as short-circuit diffusion channel for the diffusion of Al from alloy matrix to surface,and also provide nucleation sites for B2-NiAl phase,which ensure the continuous formation of Al_(2)O_(3) scale.

Interactive texture design and synthesis from mesh sketches

Geometry mesh introduces user control into tex- ture synthesis and editing, and brings more variations in the synthesized results. But still two problems related remain in need of better solutions. One problem is generating the meshes with desired size and pattern efficiently from easier user inputs. The other problem is improving the quality of synthesized results with mesh information. We present a new two-step texture design and synthesis method that addresses these two problems. Besides example texture, a small piece of mesh sketch drawn by hand or detected from example texture is input to our algorithm. And then a mesh synthesis method of geometry space is provided to avoid optimizations cell by cell. Distance and orientation features are introduced to im- prove the quality of mesh rasterization. Results show that with our method, users can design and synthesize textures from mesh sketches easily and interactively.

Chinese guidelines for the application of colon cancer staging recognition systems based on artificial intelligence platforms (2021)

The incidence and mortality of colon cancer in China are increasing each year.At present,treatment selection for colon cancer patients mainly depends on imaging results,which require a large number of radiologists to interpret.In China,there is a shortage and uneven distribution of experienced radiologists,which leads to delays and bias in the evaluation of imaging data.Based on these considerations,the Colorectal Surgery Group of the Surgery Branch of the Chinese Medical Association in collaboration with experts at Beihang University has independently developed an artificial intelligence(AI)-based recognition system for the preoperative determination of colon cancer stage to partially replace the work of and relieve the pressure on radiologists.These guidelines aim to standardize the use of AI-based recognition systems in the preoperative staging of colon cancer and guide their clinical application.

Real-Time Laparoscopic Cholecystectomy Simulation Using a Particle-Based Physical System

Laparoscopic cholecystectomy is used to treat cholecystitis and cholelithiasis.Because the high risk of the surgery prevents novice doctors from practicing it on real patients,VR-based surgical simulation has been developed to simulate surgical procedures to train surgeons without patients,cadavers,or animals.In this study,we propose a real-time system designed to provide plausible visual and tactile simulation of the main surgical procedures.To achieve this,the physical properties of organs are modeled by particles,and cluster-based shape matching is used to simulate soft deformation.The haptic interaction between tools and soft tissue is modeled as a collision between a capsule and particles.Constraint-based haptic rendering is used to generate feedback force and the non-penetrating position of the virtual tool.The proposed system can simulate the major steps of laparoscopic cholecystectomy,such as the anatomy of Calot’s triangle,clipping of the cystic duct and biliary artery,disjunction of the cystic duct and biliary artery,and separation of the gallbladder bed.The experimental results show that haptic rendering can be performed at a high frequency(>900 Hz),whereas mesh skinning and graphics rendering can be performed at 60 frames per second(fps).