Application of three-dimensional (3D) magnetic resonance (MR) Multi-Echo iN Steady-state Acquisition sequences in preoperative evaluation of lumbar disc herniation: a prospective study.

Background: Conventional spinal magnetic resonance imaging (MRI) cannot provide accurate diagnosis and surgical planning; thin-layer scanning can enhance the diagnostic efficacy. This study aimed to investigate the value of 3-dimensional (3D) magnetic resonance (MR) in preoperative evaluation of lumbar disc herniation, with a focus on the application of Multi-Echo iN Steady-state Acquisition (MENSA) sequence.

Methods: A total of 51 patients who underwent lumbar disc herniation surgery in West China Hospital of Sichuan University from June 2021 to December 2021 were prospectively enrolled. A cross-sectional study was conducted on those patients. The Cube group was scanned using 3D-FSE-Cube sequence, the Cube stir group was scanned using 3D-FSE-Cube Short Tau Inversion Recovery (STIR) sequence, and the MENSA group was scanned using MENSA sequence. Signal and noise values of nerve, herniated disc, ligamentum flavum (LF), and soft tissue were measured on the 3 groups. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Objective scores were calculated by analysis of variance (ANOVA). Image quality was scored by a 5-point method. Friedman test was used to compare subjective scores, and Kappa test was used to evaluate the consistency of 2 readers' scores.

Results: The nerve root SNRs in the MENSA and Cube stir groups were higher than that in the Cube group (P<0.01), but there was no substantial statistical difference between the 2 groups. The herniated disc and LF SNRs of the MENSA group were greater than those of the Cube stir and Cube groups (P<0.01). Soft tissue SNR was greater in the MENSA group compared with the Cube stir group (P<0.01), which was greater than the SNR in the Cube group (P<0.01). The nerve root CNR of the Cube group (102.88±73.19) was greater than that of the MENSA group (55.98±25.26, P<0.01), which was higher than the CNR in the Cube Stir group (29.42±16.22, P<0.01). The herniated disc CNR was higher in the MENSA and Cube groups than that in the Cube Stir group. The CNR of LF was greater in the MENSA group (37.71±16.87) compared to the Cube group (29.76±25.73, P=0.03), which was greater than that in the Cube stir group (10.50±7.75, P<0.01). Among the subjective ratings of 2 reviewers, MENSA sequence scored highest in the qualitative measures of image quality. In the consistency test, the Kappa values of 2 readers for 3 groups of images were all greater than 0.73, indicating good consistency. The differences of subjective scores among all groups were statistically significant (P<0.05). Overall, it was indicated that the consistency test results of the 2 readers were statistically significant and consistent. The MENSA group had the highest accuracy in diagnosing nerve compression. In addition, MENSA sequence ranked highest among the 3 sequences with 94.1% diagnostic accuracy.

Conclusions: The preoperative 3D MRI MENSA sequence can clearly depict the nerve roots and offer desirable contrast between the nerve roots, LF, bone, and intervertebral discs (IVDs). Patients with lumbar degeneration can effectively benefit from MENSA sequence since it provides useful imaging information to help understand disc herniation and compression of adjacent tissues when developing preoperative surgical strategies.