Regional T2 value differences assess lumbar disc degeneration: a 3.0-T MRI retrospective study.

OBJECTIVES

To quantify region-specific T2 relaxation dynamics in lumbar disc degeneration and evaluate their correlations with Pfirrmann grades and herniation morphology, focusing on early microstructural detection.

METHODS

This retrospective cohort study analyzed 130 lumbar discs (L1-S1) from 26 patients with single-segment disc herniation using 3.0-T MRI. T2 relaxation mapping was systematically performed with anatomical compartment segmentation defining four regions of interest: anterior annulus fibrosus, nucleus pulposus, posterior annulus fibrosus, and herniated tissue. Standardized circular ROIs (2.5-mm diameter) were applied to non-herniated regions, while herniations underwent area-matched elliptical contouring. Pfirrmann grading (I-V) was independently validated by two board-certified musculoskeletal radiologists. Statistical analyses employed nonparametric Kruskal-Wallis tests for inter-grade T2 comparisons and Spearman's rank correlation (ρ) to quantify degeneration associations.

RESULTS

Statistically significant differences in T2 values were observed across the three anatomical compartments (*p*<0.05). T2 relaxation times demonstrated an inverse correlation with Pfirrmann degeneration grades, exhibiting the strongest association in the nucleus pulposus (middle compartment; r=-0.542). This correlation intensified with advancing degeneration. Sagittal T2 comparisons revealed significant differences between Pfirrmann grade I/II and IV/V groups in all compartments, while the nucleus pulposus showed significant differences between grades I/II and III. Within identical degeneration grades, nucleus pulposus T2 values exceeded those of the anterior annulus fibrosus. Specifically, in Pfirrmann I/II discs, posterior annulus values surpassed anterior annulus values, whereas in grade IV/V discs, nucleus pulposus values exceeded posterior annulus values, with no significant anterior-posterior difference. Cross-sectionally, the nucleus pulposus exhibited the highest T2 values, while herniated tissue demonstrated the lowest.

CONCLUSIONS

Region-specific T2 mapping demonstrates potential for detecting early microstructural degeneration within lumbar intervertebral discs.