(A) method for realistic rendering of contrast medium for real-time angiography simulation

Abstract

This paper proposes a method for realistic rendering of contrast medium for real-time angiography simulation. The behavior of contrast medium and blood flow is modeled using smoothed particle hydrodynamics (SPH). A model of collision detection and response is constructed with an implicit surface function. The collision point is approximated using linear interpolation of the values of the implicit function before and after the collision. A normal vector of the surface is computed at the approximated collision point. Magnitude percent of error vector of a unit normal vector between the approximated collision point and the exact collision point is 0.04%. Computational load is reduced from 33ms to 10ms in comparison with the boundary conditions composed of the wall particles. Average computation time for position update and collision response per particle is $6.4 \times 10^{-2} ms$ for the collision model with implicit surface function and $6.8 \times 10^{-2} ms$ for the collision model with recursive mesh model AABB. Contrast medium behavior in turbulent pulsatile blood flow is simulated. Computational fluid dynamics (CFD) simulation is conducted for the ascending aorta and coronary arteries with inflow conditions corresponding to the human cardiac cycle. Boundary layer effect is simulated by the analytic calculation of the viscous boundary layer and CFD result of pressure and shear stress applied by the vessel wall. Vorticity confinement force is added to the contrast medium particle in order to compensate for the numerical dissipation of SPH fluid simulation. Comparison with real angiography X-ray image of the proposed method and the prior method is conducted with structural similarity (SSIM) to evaluate realism of the rendered X-ray images.