Bi-exponential T2* analysis of healthy and diseased Achilles tendons: an in vivo preliminary magnetic resonance study and correlation with clinical score

OBJECTIVE: To compare mono- and bi-exponential T(2)* analysis in healthy and degenerated Achilles tendons using a recently introduced magnetic resonance variable-echo-time sequence (vTE) for T(2)* mapping. METHODS: Ten 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 [T(2)*(m), short T(2)* component (T(2)*(s)) and long T(2)* component (T(2)*(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 T(2)* values. RESULTS: The means for both T(2)*(m) and T(2)*(s) were statistically significantly different between patients and volunteers; however, for T(2)*(s), the P value was lower. In patients, the Pearson correlation coefficient between ATRS and T(2)*s was −0.816 (P = 0.007). CONCLUSION: The 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 T(2)* 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