Purpose:
The purpose of this study was to investigate T1 relaxation time of the human
Achilles tendon, to test its short-term repeatability as well as the minimal detectable change, and to
assess the extent that correlate with clinical symptoms.
Methods:
Twenty asymptomatic volunteers and eighteen patients with clinically and sonographically
confirmed tendinopathy were scanned for ankle using a 3 Tesla (T) MR scanner. T1 maps
were calculated from a variable flip angle gradient echo Ultra-short echo time sequence (VFA-GE
UTE) and inversion recovery spin echo sequence (IR-SE) using a self-developed matlab algorithm
in three regions of interest of Achilles Tendon (AT). Signal to Noise Ratio (SNR) between the two
sequences was evaluated. INTRA-class Correlation Coefficient (ICC), Coefficient of Variation
(CV) and the Least Significant Change (LSC) were calculated, to test short-term repeatability of
T1. Subjects were assessed by the VISA-A clinical score. P values less than 0.005 were considered
statistically significant.
Results:
Mean T1 values were 427.09 ± 53.37 ms and 528.70 ± 103.50 ms using IR-SE sequence
and 575.43 ± 110.60 ms and 875.81 ± 425.77 ms with VFA-GE UTE sequence in the whole AT for
volunteers and patients, respectively.
:
T1 values showed a significant difference between volunteers and patients (P=0.001). Regional
variation of T1 in healthy and tendinopathic AT were greater for VFA-GE UTE sequence than for
IR-SE sequence. VFA-GE UTE sequence showed clearly higher SNR compared to IR-SE sequence.
Short-term repeatability of T1 values for volunteers showed an LSC of 22% and 14% for
IR-SE sequence and VFA-GE UTE sequence, respectively. For patients, LSC was 14% and 5% for
IR-SE sequence and VFA-GE UTE sequence, respectively. There was no correlation between T1
and VISA-A clinical score (p>0.005).
Conclusion:
VFA-GE UTE sequence used for T1 mapping calculation demonstrated short acquisition
time and clearly high SNR. Results revealed that T1 relaxation time can be used as a biomarker
to differentiate between healthy and pathologic Achilles tendon. However, T1 showed no
correlation with the VISA-A clinical score.
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