Twice Refocused Inner Volume EPI DTI of the Spinal Cord: Initial Findings

Introduction Diffusion tensor imaging of the spinal cord is challenging due to the required high resolution, the susceptibility differences of the involved tissues and the pulsation of the surrounding CSF. Single shot Echo-Planar Imaging (EPI) is the method of choice, but has the drawback of being sensitive to local gradients when long readout trains are used. The readout train can be shorten by using inner volume (IV) techniques [1]. The disadvantage of IV techniques is their low time efficiency because of the inability of multislice acquisitions. Jeong et al. [2] propose to apply a second refocusing 180° pulse in phase direction after the EPI readout train to recover the magnetization in the not measured slices. The second 180° inversion pulse can already be applied in the diffusion preparation when using a twice refocused spin echo (TRSE) preparation. In this work such a sequence is used to measure fractional anisotropy (FA) and mean diffusity (ADC) values using a probabilistic voxel classification approach [3].