Quantitative synthetic MRI for evaluation of the lumbar intervertebral disk degeneration in patients with chronic low back pain

Purpose: To verify the feasibility of synthetic MRI in quantitative evaluation of lumbar intervertebral disk (IVD) degeneration, as compared to the conventional CarrPurcell-Meiboom-Gill (CPMG) T2 mapping approach. Methods: Twenty-four patients with chronic low back pain participated in this study. Patients underwent routine lumbar MRI, CPMG T2 mapping, and synthetic MRI (MAGiC) acquisition. The degree of IVD degeneration was derived from T2-weighted images according to the Pfirrmann classification. The correlation between two T2 measurements was assessed by Pearson correlation and Bland-Altman analysis. Statistical differences of quantitative values obtained from MAGiC data across different degeneration grades were quantified by one-way ANOVA. ROC curves were used to test the sensitivity and specificity of CPMG and MAGiC T2 measurements for assessing Pfirrmann grading. Results: T2 values obtained from CPMG and MAGiC data exhibited strong positive correlation (r = 0.962, p < 0.01). Significant negative correlations were found between quantitative values (p < 0.05) and the Pfirrmann grading. Quantitative values show significant difference across Pfirrmann grading groups (one-way ANOVA, p < 0.001). Additionally, post-hoc tests show significant differences of T1 and T2 between adjacent groups among grades I-IV (p < 0.05), while the significant differences of PD were only observed between adjacent groups among grades II-IV (p < 0.05). There is no significant difference between AUCs of T2 values obtained from CPMG and MAGiC data in differentiating grade I/ II, grade II/ III and grade III/IV. Conclusions: The synthetic MRI may be used to provide quantitative biomarkers for assessing the level of lumbar intervertebral disc degeneration.