We are currently developing methods for high spatial and angular resolution diffusion tensor imaging (DTI) in humans. The goal is to develop high angular resolution diffusion weighted pulse sequence that is more accurate than traditional methods and increase the sensitivity to diffusion, thus allowing better characterization of local tissue diffusion properties.
High resolution, low distortion DTI remains one of the major challenges in MR pulse sequence development. In order to reduce the deleterious effects of the significant physiological motion in the human brain, single shot, slice selective (i.e., 2D) EPI has been widely adopted as the standard imaging sequence for human in vivo diffusion MRI.
However, this limits the attainable spatial resolution, and is prone to susceptibility artifacts that significantly distort the images. In order to overcome these limitations in existing methods, we have developed a novel 3D DTI sequence capable of obtaining high spatial resolution data that employs fast spin echoes, and is thus both time efficient and insensitive to field in homogeneities.
A novel high resolution, low distortion 3D Variable Density Spiral (VDS) Fast Spin Echo (FSE) diffusion tensor imaging (DTI) pulse sequence was developed that allows higher spatial and angular resolution DTI and is able to image in regions of the human brain previously unattainable due to susceptibility distortions. This sequence employs a novel method for eddy current correction that obviates the need for eddy current compensating pulses in the sequence that produce long echo time which enhance susceptibility-related distortions. It also employs a novel motion correction scheme that reduces artifacts due to subject motion in between excitations. In addition, because it is a spin echo sequence, no field mapping is required.
Frank LR, Jung Y, Inati S, Tyszka JM, Wong EC. High efficiency, low distortion, 3D diffusion tensor imaging with variable density spiral fast spin echoes (3D DW VDS RARE). Neuroimage, 49: 1510-23, 2010.
Tyszka JM, Frank LR. High-field diffusion MR histology: Image-based correction of eddy current ghosts in diffusion-weighted rapid acquisition with relaxation enhancement (DW-RARE). Magn Reson Med, 61: 728-33, 2009.