D.N. Metaxas and L. Axel (Eds.): FIMH 2011, LNCS 6666, pp. 95–104, 2011. © Springer-Verlag Berlin Heidelberg 2011 Simulation of Diffusion Anisotropy in DTI for Virtual Cardiac Fiber Structure Lihui Wang 1,2 , Yue-Min Zhu 2 , Hongying Li 2 , Wanyu Liu 1,2 , and Isabelle E. Magnin 2 1 Harbin Institute of Technology, 150001, Harbin, China 2 CREATIS, CNRS UMR5220, Inserm U1044, INSA Lyon, University of Lyon1, University of Lyon. 69100 Villeurbanne, France {lihui.wang,yuemin.zhu,hongying.li, isabelle.magnin}@creatis.insa-lyon.fr wanyu.liu@hit.edu.cn Abstract. 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. Keywords: DTI, cardiac myocyte, diffusion anisotropy, myocardial fiber, Monte Carlo simulation. 1 Introduction The myocardial fiber structure plays an important role in determining the mechanical and electrical properties of the ventricles of the human heart. It is very useful for analyzing the normal and pathologic states of the heart. Up to now, most research on myocardial fiber structure focuses on fiber orientation, which can be provided by diffusion magnetic resonance imaging (DMRI). DMRI measures the displacement of water molecules subject to Brownian motion within the tissues. Since the mobility of the molecules is conditioned by the microstructure of the tissue, especially the direction, we can infer the structural orientation information of the later from the anisotropy of the molecular displacements. A number of approaches for analyzing the DMRI have been proposed, and the most popular ones are diffusion tensor magnetic resonance imaging (DTI) [1, 2], high angular resolution diffusion imaging (HARDI) [3], q-space imaging (QSI) [4] and