Effects of repetitive freeze–thawing cycles on T2 and T2* of the Achilles tendon

Abstract

IntroductionIn this study we sought to evaluate the effects of multiple freezing and thawing cycles on two MR parameters to study Achilles tendon, T2 and T2*. Materials and methodsFour fresh Achilles tendons were imaged on a 3T clinical scanner and again after 1, 2, 4, and 5 freeze–thaw cycles with spin-echo (SE) and ultrashort echo time (UTE) sequences. Regions of interest were manually drawn over the entire Achilles tendon and mono-exponential curves were used to determine T2 and T2* relaxation times. ResultsThere was no statistically significant difference in mean T2 or T2* values between the fresh specimens and after subsequent cycles of freeze–thaw treatment (p>0.1). Linear regression between SE T2 values at baseline and after successive freeze–thaw cycles demonstrated moderate agreement (r=0.60) whereas UTE T2* values at baseline and after successive-freeze thaw cycles demonstrated strong agreement (r=0.92). ConclusionThese findings suggest that changes between specimens seen in vitro are due to factors other than frozen storage. Furthermore, our results suggest that there is stronger agreement between baseline (fresh) and successive freeze–thaw T2* values of tendon obtained with the UTE technique in comparison to T2 values obtained with a conventional clinical CPMG technique.