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Interventional Neuroradiology Training

Objective: Stroke is the third leading cause of death in the US. Each year, more than 750, 000 strokes result in over 150, 000 deaths. The main therapy for ischemic stroke is catheterization,allowing direct lytic therapy to dissolve the clot and restore the flow. Following femoral arterial puncture, a guidewire-catheter combination is advanced under fluoroscopic guidance through the iliac arteries, into the aortic arch, and inside the common carotid artery. This allows entry into the internal carotid artery and the cerebral circulations in the brain. This guidance is provided by intravascular angiogram, obtained during contrast agent (CA) propagation, which defines the abnormal areas, guides the instrument movement, and verifies the treatment. Because the treatment is delivered only under image-based guidance, the dedicated skill of instrument navigation and the thorough understanding of vascular anatomy are critical to avoid irreversible complications. In 2004, a decision by the FDA regarding appropriate levels of training for physicians who perform high-risk procedures in the cerebral circulation mandated that physicians train to proficiency before treating humans.


Recently, interventional radiology (another important minimally-invasive alternative to surgery) has been the focus of both commercial training systems and research work. The rationale for developing simulators for this type of procedure is similar to laparoscopic surgery. Procedures are rather technical, using indirect vision of the operative field (in this case through X-ray imaging) and flexible devices introduced through the vascular system. Real-time computation of deformable structures, fast collision detection, complex contact processing, advanced rendering techniques, and physiological modeling, are also needed. However, the problems raised are different and in many instances, complementary of the problems related to laparoscopic surgery simulation. Nowinski et al. (Nowinski et al., 2001) developed the NeuroCath system, an interventional neuroradiology pretreatment planning system that provides integrated functionalities for both training and patient-specific planning. In this system the catheter is simulated using a linear finite element model. The visual realism of the simulation is not very convincing, and physiological aspects of the simulation are not described. The interventional cardiology training system ICTS (Dawson et al., 2000) is a computer-based simulator that incorporates synthetic fluoroscopy, real-time three-dimensional interactive anatomic display, and coronary catheterization and angiography using actual catheters. The catheter simulation is based on a multi-body dynamics system. Blood flow distribution in the vascular network is also modeled as simple laminar flow. The system led to the Procedicus VIST system (Mentice) which is among the most successful commercial products in the field of computer-based medical simulation. Yet this system includes a limited representation of the vascular anatomy, and offers a simulation of fluoroscopic images of reduced quality. The Catheter Instruction System CathI (Hoefer et al., 2002) is another computer-based training system which provides force-feedback for guidewire and catheter manipulation. The system is aimed at cardiac procedures and includes a morphologically correct coronary artery model. In (Duriez et al., 2006a) and (Cotin et al., 2007) we proposed a series of solutions for developing a high-fidelity training system for interventional radiology. We particularly focused on the modeling of contacts between flexible devices (catheters, guidewires, coils) and the inner surface of vessels. We also proposed numerous improvements to the modeling of flow and contrast agent propagation. Advanced techniques were also used to improve visual feedback, by relying on volume rendering for instance. A prototype of the simulator, integrating all these different algorithms, was developed in close collaboration with interventional radiologists. A real-time simulation of interventional radiology procedures is described by Wang et al. (Wang et al., 2007), which deploys an efficient physics-based thread model to simulate the elastic behavior of guidewires and catheters. A fast collision detection scheme provides continuous collision response, which reveals more details of arterial walls than a centerline approach. The simulation is updated at a rate of 500 Hz to provide haptic feedback.

Articles related to this project
- New Approaches to Catheter Navigation for Interventional Radiology Simulation (PDF)
- A more detailed version of the previous paper, published in Computer Assister Surgery (2007)
- A Segmentation and Reconstruction Technique for 3D Vascular Structures (PDF)

Some of our current results (obtained using the SOFA framework)
Bla bla.
VIDEO: overview of the EVE simulation. Movie in Mpeg4 format.
VIDEO: animation of coil embolization procedure. Movie in Mpeg format.
VIDEO: coil deployment in a synthetic aneurysm. Movie in AVI DIVX format.

Interactive Planning of Coil Embolization