A realistic vascular model for BOLD signal up to 16.4 T

Introduction The blood oxygenation level-dependent (BOLD) signal using functional magnetic resonance imaging (fMRI) is currently the most popular imaging method to study brain function non-invasively. The sensitivity of the BOLD signal to different types of MRI sequences and vessel sizes is currently under investigation [1]. Gradient echo (GRE) sequences are known to be sensitive to larger vessels (venules and veins), whereas spin-echo (SE) sequences are generally more sensitive to smaller vessels (venules and capillaries), especially at high magnetic field strength [2, 3]. However, the widely used single vessel model is only an approximation to the realistic vascular distribution. Realistic vascular models have been proposed by Marques and Bowtell [4] and, recently, by Chen et al.[5]. We herein present a realistic vascular model (RVM) where diffusion is accounted for by a Monte-Carlo random walk.