T2 and t2* relaxometry of cartilage at the wrist joint: a comparative study of 3t and 7t mri

MRI of the wrist is one of the most challenging anatomic areas to be examined by MRI due to the small size of tissues including the thin articular cartilage at multiple locations and the triangular fibrocartilage complex (TFCC) with its complex anatomy. Conventional MRI depicts morphologic degenerative changes at the cartilage and at the TFCC usually only at advanced stages of disease. Compositional MRI is able to characterize biochemical tissue properties much earlier than morphologic changes. T2 and T2* relaxometry (“mapping”) represent two widely applied techniques, which enable non-invasive quantification of tissues’ water content and assessment of collagen content and organization. Both techniques may benefit from higher magnetic field strengths due to a better visualization of small anatomical structures caused by higher contrast-to-noise and signal-to-noise ratios. To analyze regional variations of T2 and T2* relaxation times in wrist joint cartilage and the TFCC at 3T and at 7T and to compare both field strengths. 25 healthy controls and 25 patients with chronic wrist pain were examined at 3T and 7T MRI on the same day using multi-echo-spin-echo (MESE)or gradient echo (MEGE) T2- and T2*-weighted sequences. 6 different regions of interest (ROI) were evaluated for cartilage and 3 ROIs at the TFCC based on manual segmentation (Figure 1). Paired t-test was used for comparing T2 and T2* values between field strengths and between different ROIs. Spearman's rank correlation was calculated for correlation of T2 and T2* time values between 3T and 7T. T2 and T2* time values of the cartilage differed significantly between 3T and 7T for all ROIs assessed, with one exception. At the TFCC, no significant differences were observed for T2 values between field strengths. T2* values differed significantly between 3T and 7T for all ROIs of the TFCC. The Spearman's rank correlation between 3T and 7T ranged from 0.03 to 0.62 for T2 and from 0.01 to 0.48 for T2* values (Table 1). T2 and T2* values of cartilage varied between anatomic locations in controls at 3T and at 7T (Table 2). Quantitative results of T2 and T2* mapping at the wrist differ between field strengths and show a poor correlation. Local variations for cartilage T2 and T2* time values are observed in healthy subjects.