# Angiography Simulation and Planning Using a Multi-Fluid Approach
## 1 Introduction  
Cardiovascular diseases are the number-one cause of death in the developed world. Endovascular intervention is a modern treatment to the condition with advantages of limited hemorrhage, minimal wound, faster recovery, and fewer complications compared with traditional open surgery [1]. Angiography is an essential examination procedure in endovascular interventions to obtain clear medical images of lesion locations to assess the cardiovascular damage, and to identify the location of tumors and peripheral vascular narrowing [2]. Training of angiography and indeed endovascular interventions in general is a big challenge, due to limited training resources and the complexity of the procedure. Virtual reality-based training has become an alternative for medical training. With computer-based simulators, students can practice some basic skills repeatedly with multiple medical cases and computerized objective assessments. However, the simulation realism (i.e., how well the simulation results can closely represent the real-life cases) remains a big challenge. The realism of virtual reality-based training systems is determined by simulation software and hardware system (e.g., haptics and physical feedback). This paper addressed the challenge from both software and hardware aspects. [PERSON] et al. [3] mainly focused on training techniques before angiography and proposed a simulator for Seldinger technique, in which a simulated pulse was included for needle puncture palpation andtwo haptic devices were used for the insertion of guidewire and catheter. [PERSON] et al. [4] modelled catheters using a finite element model (FEM) and adopted Poiseuille's law to compute the vascular flow with an advection equation for contrast media propagation. [PERSON] et al. [5] have taken into account the [PERSON]'s laws and other main properties of guidewires and used centerlines for contrast media propagation. These previous works, however, have not dealt with the influence of contrast media injection dosage, injection speed, and dynamic interactions between the complex two-fluids flow and complex vascular structures, which are important aspects for realistic angiography simulations. A syringe device with a constant injection speed has been described in [6], the contrast media was modelled as radius-adaptive particles along vascular centerlines, and the propagation of the particles was controlled under the blood flow via Poisseuille's law, but the simulation was limited with a constant injection speed. Validation of simulation-based training systems by medical doctors who are the end users of the systems are critical for any system to be adopted in clinic practice. The commercial simulator \"Vascular Interventional System Trainer (VIST)\" has been evaluated by physicians [7; 8]. This simulator consists of a mannequin, two monitors, joysticks for controlling fluoroscopy and a syringe for the injection of contrast media. From a recent related patent [9] of this system, the blood vessel was constructed as several vessel segments by an arranged hierarchy, such as unilateral stenosis of blood vesselswhich hardly presents the complex property of blood vessels. Furthermore, the diffusion simulation of the contrast media was implemented by a mapping table executed in a pre-processor with pre-designed and segmented blood vessels. Although this method can quickly simulate a plausible angiography effect, it is hard to simulate and analyze the statue of the fluid flow at complex lesion locations in real blood vessels using this method. In our prior work [10; 11], we have used patient blood vessel models generated from 3D rotational X-ray images in a DICOM dataset. Patient specific data-sets are helpful for training and pre-operative planning. Virtual contrast media was created by injecting air through a syringe without the simulation of force feedback. [PERSON] et al. [12] proposed a \"CATHI-system\". [PERSON] et al.