Clinical implementation of accelerated T2 mapping: Quantitative magnetic resonance imaging as a biomarker for annular tear and lumbar disc herniation

Abstract

Objectives: This study evaluates GRAPPATINI, an accelerated T₂ mapping sequence combining undersampling and model-based reconstruction to facilitate the clinical implementation of T₂ mapping of the lumbar intervertebral disc.

Methods: Fifty-eight individuals (26 females, 32 males, age 23.3 ± 8.0 years) were prospectively examined at 3 T. This cohort study consisted of 19 patients, 20 rowers, and 19 volunteers. GRAPPATINI was conducted with the same parameters as a conventional 2D multi-echo spin-echo (MESE) sequence in 02:27 min instead of 13:18 min. Additional T₂ maps were calculated after discarding the first echo (T_2-WO1ST) and only using even echoes (T_2-EVEN). Segmentation was done on the four most central slices. The resulting T₂ values were compared for all four measurements.

Results: T_2-GRAPPATINI, T_2-MESE, T_2-EVEN, and T_2-WO1ST of the nucleus pulposus of normal discs differed significantly from those of bulging discs or herniated discs (all p < 0.001). For the posterior annular region, only T_2-GRAPPATINI showed a significant difference (p = 0.011) between normal and herniated discs. There was a significant difference between T_2-GRAPPATINI, T_2-MESE, T_2-EVEN, and T_2-WO1ST of discs with and without an annular tear for the nucleus pulposus (all p < 0.001). The nucleus pulposus' T₂ at different degeneration states showed significant differences between all group comparisons of Pfirrmann grades for T_2-GRAPPATINI (p = 0.000-0.018), T_2-MESE (p = 0.000-0.015), T_2-EVEN (p = 0.000-0.019), and T_2-WO1ST (p = 0.000-0.015).

Conclusions: GRAPPATINI facilitates the use of T₂ values as quantitative imaging biomarkers to detect disc pathologies such as degeneration, lumbar disc herniation, and annular tears while simultaneously shortening the acquisition time from 13:18 to 2:27 min.

Key points: • T_2-GRAPPATINI, T_2-MESE, T_2-EVEN, and T_2-WO1ST of the nucleus pulposus of normal discs differed significantly from those of discs with bulging or herniation (all p < 0.001). • The investigated T₂ mapping techniques differed significantly in discs with and without annular tearing (all p < 0.001). • The nucleus pulposus' T₂ showed significant differences between different stages of degeneration in all group comparisons for T_2-GRAPPATINI (p = 0.000-0.018), T_2-MESE (p = 0.000-0.015), T_2-EVEN (p = 0.000-0.019), and T_2-WO1ST (p = 0.000-0.015).

Keywords: Intervertebral disc; Intervertebral disc degeneration; Intervertebral disc displacement; Spine.