Advances in diffusion MRI acquisition and processing in the Human Connectome Project

The Human Connectome Project (HCP) is a collaborative 5-year effort to map human brain connections and their variability in healthy adults. A consortium of HCP investigators will study a population of 1200 healthy adults using multiple imaging modalities, along with extensive behavioral and genetic data. In this overview, we focus on diffusion MRI (dMRI) and the structural connectivity aspect of the project. We present recent advances in acquisition and processing that allow us to obtain very high-quality in-vivo MRI data, whilst enabling scanning of a very large number of subjects. These advances result from 2 years of intensive efforts in optimising many aspects of data acquisition and processing during the piloting phase of the project. The data quality and methods described here are representative of the datasets and processing pipelines that will be made freely available to the community at quarterly intervals, beginning in 2013

Real-Time 3D Image Registration for Functional MRI

Subject head movements are one of the main practical difficulties with brain functional MRI. A fast accurate method for rotating and shifting a 3D image using a shear factorization of the rotation matrix is described. Combined with gradient descent (repeated linearization) on a least squares objective function, 3D image realignment for small movements can be computed as rapidly as whole brain images can be acquired on current scanners. INTRODUCTION Subject head movements are a major problem with brain functional MRI. If two neighboring voxels differ in intrinsic brightness by 20%, then a motion of 10% of a voxel dimension can result in a 2% signal change---comparable to the BOLD signal change at 1.5 Tesla, subsequent to neural activation (1). If the movements occur synchronously with the task/stimulus alternation, false activations may be detected (2). If the movements are uncorrelated with the task/stimulus alternation, the motion-induced signal changes can interfere with the detect..