Voxel-wise group analysis of DTI

Diffusion tensor MRI (DTI) is now a widely used modality to investigate the fiber tissues in vivo, especially the white matter in brain. An automatic pipeline is described in this paper to conduct a localized voxel-wise multiple-subject group comparison study of DTI. The pipeline consists of 3 steps: (1) Preprocessing, including image format converting, image quality check, eddy-current and motion artifact correction, skull stripping and tensor image estimation, (2) study-specific unbiased DTI atlas computation via affine followed by fluid nonlinear registration and warping of all individual DTI images into the common atlas space to achieve voxel-wise correspondence, (3) voxel-wise statistical analysis via heterogeneous linear regression and wild bootstrap technique for correcting for multiple comparisons. This pipeline was applied to process data from a fitness and aging study and preliminary results are presented. The results show that this fully automatic pipeline is suitable for voxel-wise group DTI analysis.

1. INTRODUCTION

Diffusion Tensor Magnetic Resonance Imaging (DT-MRI, DTI) [1] is a relatively new but rather fast developing MR imaging modality, aiming to measure the diffusivity of water in tissue. DTIs have been widely used to investigate white matter microstructure and its changes in brain, in vivo including normal brain development, aging and pathological damages. Unlike traditional medical images, DTI at each voxel is a symmetric positive definite matrix with 6 independent elements. Then, scalar indices, such as fractional anisotropy (FA), mean diffusivity (MD) and eigenvalues, can be calculated from a tensor. Due to the complexity of tensor images, the processing and analysis of DTI is still under extensive research.