Regional Variations of T₂* in Healthy and Pathologic Achilles Tendon in Vivo at 7 Tesla: Preliminary Results

The aim of this study was to investigate T₂* in the Achilles tendon (AT), in vivo, using a three-dimensional ultrashort time echo (3D-UTE) sequence, to compare field strength differences (3 and 7 T) and to evaluate a regional variation of T₂* in healthy and pathologic tendon. Ten volunteers with no history of pain in the AT and five patients with chronic Achilles tendinopathy were recruited. 3D-UTE images were measured with the following echo times, at echo time = [0.07, 0.2, 0.33, 0.46, 0.59, 0.74, 1.0, 1.5, 2.0, 4.0, 6.0, and 9.0 ms]. T₂* values in the AT were calculated by fitting the signal decay to biexponential function. Comparing volunteers between 3 and 7 T, short component T(2s)* was 0.71 ± 0.17 ms and 0.34 ± 0.09 ms (P < 0.05); bulk long component T(2l)* was 12.85 ± 1.87 ms and 10.28 ± 2.28 ms (P < 0.05). In patients at 7 T, bulk T(2s)* was 0.53 ± 0.17 ms (P = 0.045, compared to volunteers), T(2l)* was 11.49 ± 4.28 ms (P = 0.99, compared to volunteers). The results of this study suggest that the regional variability of AT can be quantified by T₂* in in vivo conditions. Advanced quantitative imaging of the human AT using a 3D-UTE sequence may provide additional information to standard clinical imaging. Finally, as the preliminary patient data suggest, T(2s)* may be a promising marker for the diagnosis of pathological changes in the AT.