ObjectiveTo compare mono- and bi-exponential T2* analysis in healthy and degenerated Achilles tendons using a recently introduced magnetic resonance variable-echo-time sequence (vTE) for T2* mapping.MethodsTen volunteers and ten patients were included in the study. A variable-echo-time sequence was used with 20 echo times. Images were post-processed with both techniques, mono- and bi-exponential [T2*m, short T2* component (T2*s) and long T2* component (T2*l)]. The number of mono- and bi-exponentially decaying pixels in each region of interest was expressed as a ratio (B/M). Patients were clinically assessed with the Achilles Tendon Rupture Score (ATRS), and these values were correlated with the T2* values.ResultsThe means for both T2*m and T2*s were statistically significantly different between patients and volunteers; however, for T2*s, the P value was lower. In patients, the Pearson correlation coefficient between ATRS and T2*s was −0.816 (P = 0.007).ConclusionThe proposed variable-echo-time sequence can be successfully used as an alternative method to UTE sequences with some added benefits, such as a short imaging time along with relatively high resolution and minimised blurring artefacts, and minimised susceptibility artefacts and chemical shift artefacts. Bi-exponential T2* calculation is superior to mono-exponential in terms of statistical significance for the diagnosis of Achilles tendinopathy.Key Points• Magnetic resonance imaging offers new insight into healthy and diseased Achilles tendons• Bi-exponential T2* calculation in Achilles tendons is more beneficial than mono-exponential• A short T2* component correlates strongly with clinical score• Variable echo time sequences successfully used instead of ultrashort echo time sequences

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.

Long-term clinical outcome in patients 7.9 years after AOT was good, but did not correlate with morphological and biochemical imaging results except for T2-mapping.