In Vivo Measurement of Fast Transversal Relaxation Times of Achilles Tendon Using Ultra-High Field MRI

The aim of the study was to investigate proton transverse relaxation times combined with local magnetic field non-uniformities (T2*) of human Achilles tendon in vivo as a prospective marker for diagnosis of early pathological changes. Achilles tendon consists mainly of highly oriented collagen fibres resulting in lower water mobility, and therefore fast relaxation processes of protons. Mapping of ultra-short T2* using conventional MR techniques is considered challenging using conventional sequences. Ten volunteers and two patients with chronic tendonitis were included in the study. 3D ultra-short time echo (TE) sequence with radial sampling was used. From the images acquired at different TEs (0.07, 0.20, 0.30, 0.46, 0.59, 0.74, 1.00, 1.50 ms), T2* map was constructed by pixel-by-pixel fitting of signal intensities to mono-exponential function. Resulting maps were evaluated in various anatomical regions (tendon-muscle junction, medial part and insertion). Mean bulk T2* in volunteers was 0.56 ± 0.18 ms. In patients with chronic Achillotendonitis, T2* values were higher in comparison to healthy volunteers. Advanced quantitative imaging of human Achilles tendon has a potential to benefit from early diagnosis of degenerative processes and so prevent the development of serious tendon damage, such as partial tear or rupture.