Intervertebral disc lesions: visualisation with ultra-high field MRI at 11.7 T

Tears and fissures in the intervertebral disc are probably influencing spinal stability. Discography investigations with the aim of fissure detection have been criticised and are discouraged. Therefore, alternative imaging methods, such as MRI, must be investigated.

A custom-made device was used to insert six needles with different diameters (0.3-2.2 mm/30-14 G) into the annulus of six bovine tail discs (Cy2-Cy3). Directly after removal of the needles, the discs were scanned in an 11.7 T MRI (Res.: 0.059 × 0.059 × 0.625 mm(3), tscan: 31 min), in a 3 T MRI with a clinical and additionally with two experimental protocols (exp_HR: Res.: 0.3 mm(3), tscan: 97 min/exp_LR: Res.: 0.5 mm(3), tscan: 13.4 min). The obtained images were analysed for lesion volume and lesion length using a 3D-reconstruction software.

At 11.7 T, all lesions were visible along with the lamellar structure of the annulus. In the clinical 3 T images, no lesions were visible at all. The 3 T experimental protocols revealed 4 (exp_HR) and 2 (exp_LR) of the 6 lesions. The reconstructed lesions did not have an ideal cylindrical shape. The measured volumes of the lesions ranged from 0.7 to 13.9 mm(3) (11.7 T), 0.1-11.4 mm(3) (exp_HR) and 0.0-12.4 mm(3) (exp_LR) and correlated, but were smaller than the corresponding needle size. The lengths of all needle lesions ranged from 2.9 to 12.3 mm (11.7 T), 0.8-9.7 mm (exp_HR) and 0.0-9.7 mm (exp_LR).

Ultra-high field MRI at 11.7 T is a non-invasive tool to directly visualise annular lesions in vitro, while a 3 T MRI, even with experimental protocols and longer scanning times, demonstrates limited ability. In vivo, it is problematic with the clinical systems available today.