Shao-Hua Mi

3D modeling of coronary arteries based on tubular-enhanced CURVES segmented regions for robotic surgical simulation

The visualization of the coronary vasculature is of utmost importance in interventional cardiology. Intravascular surgical robots assist the practitioners to perform the complex procedure while protecting them from the tremendous occupational hazards. Robotic surgical simulation aims to provide support for the learners in both efficiency and convenience. The blood vessels especially the coronary arteries with rich details are the key part of the anatomic scenario of the virtual training system. The variations in diameters and directions make the segmentation of the coronary arteries a difficult work. In this paper, a robust and semi-automatic approach for the segmentation of the coronary arteries is developed. The approach is based on the multi-scale tubular enhancement and an improved geodesic active contours model. The demonstrated approach firstly enhances the tubular objects by computing their “vesselness”. Next the edge potential maps are calculated based on the enhanced information. Meanwhile, the initial contours are generated by a modified fast marching method. Then the actual wave fronts evolution extracts the details of the coronary arteries. Finally the visualization model is organized based on the segmentation results by the marching cubes method. This approach has been proved successful for the visualization of the coronary arteries based on the CTA information.

A multi-body mass-spring model for virtual reality training simulators based on a robotic guide wire operating system

Generally, surgeons of minimally invasive surgery should possess good ability to coordinate their both hands. The manipulation of guide wire is considered a core skill. Obtaining that core skill to perform minimally invasive surgery requires training. In minimally invasive surgery, a surgical robot can assist doctors to position precisely and provide stable operation platform. Therefore, to develop a virtual reality simulators for training purpose based on a robotic guide wire operating system is an important and challenging subject. In this paper, a multi-body mass-spring model for simulating guide wire is presented and evaluated. In order to overcome the disadvantage of using mass-spring approach to model the guide wire, we propose a new collision detection algorithm and a new collision response algorithm. Finally, we test our guide wire with a complex and realistic 3D vascular model, which is selected from computer tomography database of real patients. The result shows that the virtual reality training simulators is effective and promising.

A collision response algorithm for 3D virtual reality minimally invasive surgery simulator

In recent years, rapid development of minimally invasive surgery has taken place. Virtual reality simulator enables the trainees to obtain the core catheter/guide wire handling skills and to decrease the error rate of operation prior to performing them on a real patient. In this paper, we present and evaluate a collision response algorithm and a force feedback computing method for simulating a catheter/guide wire in the interactive 3D virtual realty simulator based on a robotic catheter/guide wire operating system. In order to provide a real-time virtual environment, a multi-threading technology is used to accelerate the medical simulation procedure. Finally, we test the virtual catheter/guide wire with a complex and realistic 3D vascular model, which is generated from computed tomography angiography (CTA) series in DICOM datasets captured in a actual patient. The results show that the collision response algorithm in the system is effective and promising.

A 3D virtual reality simulator for training of minimally invasive surgery

For the last decade, remarkable progress has been made in the field of cardiovascular disease treatment. However, these complex medical procedures require a combination of rich experience and technical skills. In this paper, a 3D virtual reality simulator for core skills training in minimally invasive surgery is presented. The system can generate realistic 3D vascular models segmented from patient datasets, including a beating heart, and provide a real-time computation of force and force feedback module for surgical simulation. Instruments, such as a catheter or guide wire, are represented by a multi-body mass-spring model. In addition, a realistic user interface with multiple windows and real-time 3D views are developed. Moreover, the simulator is also provided with a human-machine interaction module that gives doctors the sense of touch during the surgery training, enables them to control the motion of a virtual catheter/guide wire inside a complex vascular model. Experimental results show that the simulator is suitable for minimally invasive surgery training.

Centerlines extraction for lumen model of human vasculature for computer-aided simulation of intravascular procedures

The computer-aided surgical simulation aims to provide an economic tool of effectiveness and convenience for the training process. In building this simulation system, the construction of the virtual anatomic environment is one of the major tasks. It provides the virtual tools with the scenario in which they are manipulated by the trainee. In intravascular surgery simulation, the surface model of the blood vessels is the most important part of the virtual environment. In order to achieve better performances in the simulation of path planning and navigation, the surface model based on real patients CTA data needs further process. We proposed in this paper an approach to extract the centerlines of each segment of the image-based surface model of the blood vessels. The surface model is firstly processed to check the connectivity of the consisting polygons in order to extract the largest connected region within the surface. Next, the resulting surface is smoothed by a windowed sinc function kernel with proper parameters. After the normal vectors of the smoothed surface are computed, the surface is subdivided and the centerlines of the surface model are computed by using the power crust algorithm. The experimental results show that the approach is capable of extracting the centerlines of the vessel model.

Lumen segmentation and visualization of abdominal aorta using geodesic active contours for intravascular surgical simulation

Percutaneous transluminal coronary angioplasty (PTCA) has been proved to be a standard solution to most cardiovascular diseases (CVDs). The surgical simulator provides the trainees a new vehicle to learn this skill much more conveniently and effectively. The blood vessel model is at the core of the virtual environment. In this paper, a robust and semi-automatic approach to segment the abdominal aorta from the computed tomography angiography (CTA) is developed. The proposed approach employs the geodesic active contours method as the main component. The edge potential map is generated by applying nonlinear mapping function. The initial contours are evolved by applyging the fast marching method. The surface information representing the vessel is extracted by the marching cubes method. This approach has been proved successful for the construction of 3-D surface model of the aorta based on the CTA series.

An 3D interactive virtual reality software toolkit for minimally invasive vascular surgery

Recently, much more attention has been paid to the development of minimally invasive vascular surgery. Simulating behaviors of a catheter/guide wire in a realistic 3D vascular model for minimally invasive vascular surgery is a challenging subject. One of the main problems for an 3D computer-based virtual reality simulator is how to design a software toolkit primarily targeted to medical simulation. In this paper, we describe an 3D interactive virtual reality software toolkit and present an example of application to a virtual minimally invasive vascular surgery procedure. Finally, experimental results are given to show that the 3D interactive virtual reality software toolkit is effective and promising.

Mesh optimization of vessel surface model for computer-aided simulation of percutaneous coronary intervention

Percutaneous coronary intervention is the gold standard to coronary diseases in the past decades due to much less trauma and quick recovery. However, due to the traits of minimal invasiveness, clinicians have to defeat the difficulties in eye-hand coordination during the procedure, which also makes it a non-trivial task in the catheterization lab. The computer-aided surgical simulation is designed to provide a reliable tool for the early stage of the training of the procedure. In this simulation system, the surface model of the vessels contribute the major part in the virtual anatomic environment. On the other hand, heavy interactions between the virtual surgical tools and the model surface occur during the training. In order to achieve acceptable performances, the patient-specific vessel surface model needs further process to adapt to this situation. We proposed in this paper an approach to optimize the meshes that consist the surface model with its application in consideration. The connectivity of the surface model is firstly checked. Next a smooth processing is applied without modifying the geometry of the largest-connected surface. Then the quantities of the polygons consisting the model surface are eliminated both dramatically and appropriately. The resultant surface model is applied in the validation test interacting with the virtual guidewire.

Tree structures segmentation of coronary arteries using CURVES method for interventional surgical simulation

Visualization model of the coronary vasculature is of utmost importance for the diagnosis of the coronary heart diseases, as well as the planning and navigation of the intravascular surgery. To protect the cardiologists and operation staff against the ionizing radiation, surgical robots are designed and come to assist the practitioners during the interventional procedure. Robotic surgical simulation aims to provide effective, economic and convenient support for the learners with the surgical details as real as possible. In building this system, the geometric model of the blood vessels especially the coronary arteries are the key part of the virtual anatomic scenario. Because of the complex topologies, the segmentation of the coronary arteries is full of challenges. We developed in this paper a semi-automatic approach for this challenging work. The approach is based on an improved geodesic active contours model called CURVES. Firstly, the region that contains the whole heart in the original images are completely extracted. Secondly, the extracted volumetric data is smoothed and thresholded in order to remove noises and irrelevant details. Next the image features are generated by calculating the gradients pixel-wisely, while the initial contours are generated by a modified fast marching method. Then the contour evolution is provoked to segment the boundaries of the coronary arteries. Finally the surface model is visualized after information is organized by using the marching cubes method. Experimental results showed the capability of the proposed approach in the segmentation of the coronary arteries tree.