Ultrahigh‐resolution quantitative spinal cord MRI at 9.4T

• Published in: Magnetic resonance in medicine Vol. 85; no. 2; pp. 1013 - 1027
• Main Authors: Geldschläger, Ole, Bosch, Dario, Avdievich, Nikolai I., Henning, Anke
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01-02-2021
• Subjects: 9.4 Tesla; Brain; Brain - diagnostic imaging; Gray Matter - diagnostic imaging; high‐field magnetic resonance imaging; Humans; Image acquisition; Image contrast; Image Processing, Computer-Assisted; Image quality; Image segmentation; In vivo methods and tests; Magnetic Resonance Imaging; Mathematical analysis; Medical imaging; Noise; Relaxation time; relaxometry mapping; segmentation; Signal quality; Spinal cord; Spinal Cord - diagnostic imaging; spinal cord magnetic resonance imaging; Substantia alba; Substantia grisea; White Matter - diagnostic imaging; segmentation; relaxometry mapping; high-field magnetic resonance imaging; spinal cord magnetic resonance imaging; 9.4 Tesla
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.28455

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.