T 1 ρ and T 2 mapping for the determination of articular cartilage denaturalization with osteonecrosis of the femoral head: A prospective controlled trial

Background In the future, biochemical MRI might provide a valuable noninvasive quantitative analysis of the biochemical composition of cartilage in osteonecrosis of the femoral head (ONFH). Purpose To investigate the diagnostic performance of T 1 ρ and T 2 mapping in cartilage denaturalization with ONFH and to determine the correlation between T 1 ρ and T 2 mapping and the Association Research Circulation Osseous (ARCO) stage. Study Type Prospective. Subjects Forty‐seven patients with ONFH (stage I to III according to the ARCO criteria) and 24 volunteers (control group) were recruited for the prospective study. Sequence Conventional MRI, multiple echo recalled gradient echo (MERGE), and T 1 ρ and T 2 mapping sequences. Assessment Pseudocolor images and MERGE images were combined in the AW4.5 workstation. The region of interest (ROI) of the hip cartilage was 4–6 mm². The sagittal T 1 ρ and T 2 mapping values were calculated by the two first authors. Statistical Tests One‐way analysis of variance (ANOVA), LSD t ‐tests, Pearson correlation analysis, and receiver operator characteristic (ROC) curves. The significance level was set at P < 0.05. Results The T 1 ρ and T 2 mapping values of the ONFH group were significantly higher than the values of the control group ( P  = 0.000). Regarding the assessment of the severity of ARCO staging, both T 1 ρ ( r  = 0.66, P  = 0.004) and T 2 mapping ( r  = 0.501, P  = 0.002) were positively associated with disease severity. The T 1 ρ values were positively correlated with the T 2 mapping values ( r  = 0.381, P  = 0.000). The areas under the curve (AUC) for the T 1 ρ and T 2 mapping values were 0.822 and 0.791, respectively. The diagnostic sensitivity and specificity were 72.34% and 70.83% for T 1 ρ mapping and 72.34% and 58.33%, respectively, for T 2 mapping. Data Conclusion Both T 1 ρ and T 2 mapping performed well in diagnosing the cartilage denaturalization in ARCO stage I‐III ONFH patients. T 1 ρ mapping had a higher diagnostic sensitivity and specificity than T 2 mapping. Level of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:760–767.