Ultrahigh-resolution quantitative spinal cord MRI at 9.4T

Purpose: To present the results of the first human spinal cord in vivo MRI scans at 9.4T. Methods: A human brain coil was used to image the human spinal cord at 9.4T. All anatomical images were acquired with a T₂*-weighted gradient-echo sequence. A comparison of the influence of four different B₀ shimming routines on the image quality was performed. Intrinsic signal-to-noise-ratio maps were determined using a pseudo-multiple replica approach. Measurements with different echo times were compared and processed to one multiecho data image combination image. Based on the multiecho acquisitions, T₂*-relaxation time maps were calculated. Algorithmic spinal cord detection and gray matter/white matter segmentation were tested. Results: An echo time between 9 and 13.8 ms compromised best between gray matter/white matter contrast and image quality. A maximum in-plane resolution of 0.15 × 0.15 mm² was achieved for anatomical images. These images offered excellent image quality and made small structures of the spinal cord visible. The scanner vendor implemented B₀ shimming routine performed best during this work. Intrinsic signal-to-noise-ratio values of between 6600 and 8060 at the upper cervical spinal cord were achieved. Detection and segmentation worked reliably. An average T₂*-time of 24.88 ms ± 6.68 ms for gray matter and 19.37 ms ± 8.66 ms for white matter was calculated. Conclusion: The proposed human brain coil can be used to image the spinal cord. The maximum in-plane resolution in this work was higher compared with the 7T results from the literature. The 9.4T acquisitions made the small structures of the spinal cord clearly visible.