Simulation of Diffusion Anisotropy in DTI for Virtual Cardiac Fiber Structure

Diffusion anisotropy is the most fundamental and important parameter in the description of cardiac fibers using diffusion tensor magnetic resonance imaging (DTI), by reflecting the microstructure variation of the fiber. It is, however still not clear how the diffusion anisotropy is influenced by different contiguous structures (collagen, cardiac myocyte, etc.). In this paper, a virtual cardiac fiber structure is modeled, and diffusion weighted imaging (DWI) and DTI are simulated by the Monte Carlo method at various scales. The influences of the water content ratio in the cytoplasm and the extracellular space and the membrane permeability upon diffusion anisotropy are investigated. The simulation results show that the diffusion anisotropy increases with the increase of the ratio of water content between the intracellular cytoplasm and the extracellular medium. We show also that the anisotropy decreases with the increase of myocyte membrane permeability.