Multi-parametric quantitative MRI for characterizing of lumbar intervertebral disc high-intensity zones in patients with chronic low back pain.

BACKGROUND: A high-intensity zone (HIZ) in the posterior annulus fibrosus is a critical radiological marker frequently associated with discogenic low back pain (LBP) and annular tears. Conventional MRI evaluation is inherently subjective, while quantitative MRI provides objective insights into biochemical changes within the intervertebral disc. Therefore, this cross-sectional study aimed to identify independent factors associated with HIZs and develop an integrated multivariable model combining quantitative parameters and morphological features. METHODS: Patients with chronic LBP underwent conventional lumbar MRI and multi-parametric quantitative MRI mapping. Pfirrmann grade, disc level, and structural status (normal, bulging, or herniation) were independently assessed for each intervertebral disc from L1/L2 to L5/S1. Quantitative T1, T2, and proton density (PD) values were measured in the nucleus pulposus, anterior annulus fibrosus, and posterior annulus fibrosus. Univariable and multivariable analyses based on generalized estimating equations (GEE) were performed to identify independent factors associated with HIZ. The model's discriminative performance of the model was evaluated using the area under the receiver operating characteristic curve (AUC) and variable importance analysis. RESULTS: A total of 385 intervertebral discs from 77 patients were evaluated, of which 53 (13.8%) discs were HIZ positive. Disc herniation (OR = 4.39, P = 0.010), lower disc level (L4/L5-L5/S1) (OR = 3.60, P = 0.043), and T2 values in the nucleus pulposus (T2NP) (OR = 2.46 per 10-ms decrease, P = 0.002) were identified as independent associated factors for HIZ. The integrated multivariable model yielded excellent discrimination (AUC = 0.904, 95% CI 0.871-0.935), which was confirmed by internal validation with 1000 bootstrap resamples (AUC = 0.899, 95% CI 0.889-0.905). T2NP alone also demonstrated favorable diagnostic efficacy (AUC: 0.832, 95% CI 0.789-0.874, DeLong's test P = 0.008), with a cut-off value of ≤ 60.25 ms. Variable importance analysis showed that T2NP dominated the model, accounting for 72.3% of the discriminative weight. CONCLUSION: Disc herniation, lower disc levels, and T2NP were independent associated factors for HIZs. T2NP was the predominant quantitative biomarker associated with HIZs in patients with chronic LBP, suggesting that it may reflect underlying biochemical changes more sensitively than macroscopic morphological features.