Clinical implementation of accelerated T(2) mapping: Quantitative magnetic resonance imaging as a biomarker for annular tear and lumbar disc herniation

OBJECTIVES: This study evaluates GRAPPATINI, an accelerated T(2) mapping sequence combining undersampling and model-based reconstruction to facilitate the clinical implementation of T(2) 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 T(2) 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 T(2) 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’ T(2) 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 T(2) 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 T(2) mapping techniques differed significantly in discs with and without annular tearing (all p < 0.001). • The nucleus pulposus’ T(2) 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).