The development and future of perfusion fMRI for dynamic imaging of human brain activity.
ABSTRACT Arterial spin labeled (ASL), perfusion fMRI was developed nearly simultaneously with BOLD fMRI. The application of this technique in studies of human brain activity has grown slowly over the last twenty years, primarily because of the need to meet technical challenges in data acquisition and analysis. Even within these constraints, perfusion fMRI has been identified as a tool that is well suited to measure slow changes in neural activity and to examine individual differences in brain-behavior relationships. Major advances have been made in acquisition and analysis techniques during this time. With further, anticipated technical improvements, perfusion fMRI studies in humans are poised to gain the improved cortical spatial resolution that has been observed in animal studies. If achieved, these advances portend surprising future applications of perfusion fMRI, including multi-voxel pattern analysis.
Article: Parameterisation of multi-scale continuum perfusion models from discrete vascular networks.[show abstract] [hide abstract]
ABSTRACT: Experimental data and advanced imaging techniques are increasingly enabling the extraction of detailed vascular anatomy from biological tissues. Incorporation of anatomical data within perfusion models is non-trivial, due to heterogeneous vessel density and disparate radii scales. Furthermore, previous idealised networks have assumed a spatially repeating motif or periodic canonical cell, thereby allowing for a flow solution via homogenisation. However, such periodicity is not observed throughout anatomical networks. In this study, we apply various spatial averaging methods to discrete vascular geometries in order to parameterise a continuum model of perfusion. Specifically, a multi-compartment Darcy model was used to provide vascular scale separation for the fluid flow. Permeability tensor fields were derived from both synthetic and anatomically realistic networks using (1) porosity-scaled isotropic, (2) Huyghe and Van Campen, and (3) projected-PCA methods. The Darcy pressure fields were compared via a root-mean-square error metric to an averaged Poiseuille pressure solution over the same domain. The method of Huyghe and Van Campen performed better than the other two methods in all simulations, even for relatively coarse networks. Furthermore, inter-compartment volumetric flux fields, determined using the spatially averaged discrete flux per unit pressure difference, were shown to be accurate across a range of pressure boundary conditions. This work justifies the application of continuum flow models to characterise perfusion resulting from flow in an underlying vascular network.Medical & Biological Engineering 01/2013; · 1.76 Impact Factor