Diffusion-weighted imaging of the spine with readout-segmented (RS)-EPI

Introduction: The development of diffusion-weighted imaging (DWI) of the spine has been hindered by the large off-resonance effects problematic for single-shot EPI. Overcoming these restrictions would open up applications ranging from the diagnosis of spinal cord infarction, vertebral body fractures, lymphoma, trauma, and many other disorders. Navigated interleaved EPI has been shown to overcome this distortion problem both in the brain [1] and in the spine [2]. However, interleaved EPI may lead to undersampling effects in k-space leading to ghosting [3]. Readout-segmented (RS)-EPI has recently been shown to be a promising pulse sequence for high-resolution DWI of the human brain, with significantly reduced distortions [4-6]. RS-EPI uses several ‘blinds’ (each coupled with a central blind navigator) which are adjacent in the readout direction. The shorter echo-spacing – or, in other words, the increased pseudo bandwidth along the phase encoding direction – reduces both geometric distortions and image blurring. Since each blind itself is consistent (that is, acquired at full FOV), this trajectory also avoids ghosting in the presence of motion that occurs between shots in interleaved EPI. The objective of this study was to compare DW images acquired with RS-EPI and EPI. Here we produce images with significantly reduced distortions compared with EPI.