Diffusion-weighted imaging of the spine using radial k-space trajectories

Introduction: Diffusion-weighted MR imaging (DWI) of the spine requires rob ust imaging methods, that are insensitive to susceptibility effects caused by the transition from bone to soft tissue and motion artifacts due to brea thing, swallowing, and cardiac motion. The purpose of this study was to dev elop a robust imaging method suitable for DWI of the spine. Methods and subjects: A radial k-space spin echo sequence has been implemen ted, which is self-navigating because each acquisition line passes through the origin of k-space. Influence of cardiac motion and associated flow of c erebrospinal fluid is minimized by cardiac gating with a finger photoplethy smograph. The sequence has been tested on a 1.5T system. Diffusion-weighted images of six normal volunteers were acquired in the sagittal plane with 4 b values between 50 and 500 s mm(-2). Because of the symmetries of the cor d, diffusion measurements in the head-foot (HF) or left-right (LR) directio ns were sufficient to measure the dominant effects of anisotropy. Results: The apparent diffusion coefficients (ADCs) measured, respectively, in the LR and HF directions were (0.699 +/- 0.050) x 10(-3) and (1.805 +/- 0.086) x 10(-3) mm(2) s(-1) in the spinal cord, (1.588 +/- 0.082) x 10(-3) and (1.528 +/- 0.052) x 10(-3) mm(2) s(-1) in the intervertebral disks, an d (0.346 +/- 0.047) x 10(-3) and (0.306 +/- 0.035) x 10(-3) mm(2) s(-1) in the vertebrae of the cervicothoracic spine. Conclusion: Diffusion-weighted spin echo sequences with radial trajectories in k-space provide a means of achieving robust, high quality diffusion-wei ghted imaging and measuring ADCs in the spine. The application of the diffu sion-weighting gradients in different directions allows diffusion anisotrop y to be measured. (C) 2001 Elsevier Science B.V. All rights reserved.