Quantitative T2 mapping of the sacroiliac joint cartilage at 3T in patients with axial spondyloarthropathies

To evaluate the diagnostic value of T2 mapping of sacroiliac joint cartilage in patients with axial spondyloarthropathies (SpA). Thirty-seven SpA patients and 43 controls (mean age: 36.5 ± 8.2; 20 men) prospectively underwent conventional MRI and T2 mapping of the sacroiliac joints at 3 T. SpA patients and their sacroiliac joints were categorized into active and inactive based on the presence of bone marrow edema on the conventional MRI. T2-relaxation times were measured by drawing six manual ROIs on the cartilaginous part of the joints. T2 values of the bilateral iliac and sacral joint cartilages for each patient (T2${}_{subject}$), iliac and sacral cartilages for each sacroiliac joint (T2${}_{joint}$), iliac cartilage (T2${}_{iliac}$), and sacral cartilage (T2${}_{sacral}$) were calculated and compared between SpA patients and controls, and active and inactive joints. The T2${}_{subject}$ of SpA patients (50.48 ± 5.32 ms) was significantly higher than the T2${}_{subject}$ of the controls (46.33 ± 3.30 ms, p < 0.001). Selecting an optimal T2${}_{subject}$ cut-off value of 48.77 to differentiate SpA patients from controls revealed a sensitivity and a specificity of 62.2% and 81.4% respectively (AUC = 0.739). In SpA patients, T2${}_{joint}$, T2${}_{iliac}$, and T2${}_{sacral}$ values of the inactive joints were not significantly different from those of the active joints (p = 0.088, p = 0.179, and p = 0.069). T2${}_{joint}$, T2${}_{iliac}$, and T2${}_{sacral}$ values of the inactive joints of SpA patients were significantly higher than those of the controls (p = 0.012, p = 0.029, and p = 0.016). T2 values of both active and inactive sacroiliac joint cartilages of SpA patients were increased. Thus, T2 mapping may be used in the diagnosis of SpA. Sacroiliac cartilage T2 values of SpA patients increase compared to those of the non-SpA controls. Sacroiliac cartilage T2 values of active and inactive joints of SpA patients increase compared to those of the non-SpA controls. Sacroiliac cartilage T2 values of active and inactive joints of SpA patients do not show statistically significant difference.