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

Abstract

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

Assessment of different fitting methods for in-vivo bi-component T2* analysis of human patellar tendon in magnetic resonance imaging

“…However, tendon and other musculoskeletal tissues containing abundant highly organized col- @ C I C E d i z i o n i I n t e r n a z i o n a l i lagen fibers are difficult to assess using quantitative MR techniques due to their extremely rapid signal decay. New MR techniques including ultra-short echotime (UTE) imaging 10,37,38 , variable echo time (VTE) imaging 25,39 and zero echo-time (ZTE) imaging 40,41 have been recently developed to capture the rapidly decaying signal within musculoskeletal tissues. The UTE sequence used in our study utilized a center-out twisted 3D cone k-space trajectory which has been shown to increase sampling uniformity, decrease undersampling artifact, and provide better SNR performance when compared to traditional 2D and 3D radial UTE sequences 33 .…”

“…In our study, the 3D cone UTE sequence provided complete anatomic coverage of the patellar tendon in human subjects at 3.0T with clinically feasible spatial resolutions and scan times and with an SNR of 54.5, which has been shown to be adequate to accurately estimate bi-component T2* parameters from previous literature 28 and the results of our simulation study. Recent studies have demonstrated that bi-component exponential signal models are better suited than single-component models for evaluating tendon 19,[23][24][25] .…”

“…The T2* of the two water components in tendon have varied in different studies between 0.3 ms and 1.3 ms for the short component and 8.2ms and 20.4ms for the long component 19,[23][24][25] . The differences in measured T2* parameters is likely due to multiple factors including different field strengths, vender platforms, sequence designs, imaging parameters, imaging conditions, and tendon types.…”

“…The Authors later reported that bi-component T2* parameters did not change with tensile loading of the Achilles tendon 24 . Jarus et al compared single-component and bi-component T2* analysis of the Achilles tendon in human subjects and found that the bi-component analysis provided greater diagnostic performance for distinguishing between normal and pathologic tendon 25 . However, multiple factors may affect estimations of bi-component T2 and T2* parameters within musculoskeletal tissues.…”

Effects of fat saturation on short T2 quantification

“…Often however, the MSK tissues of interest may contain structures with multiple short T2 components [8,9], which simultaneously contribute to signals in the region of interests (ROIs). Such components with different T2 values can get attenuated by varying amounts (defined here as a reduction factor Q), e.g.…”