Comparison of two ultrashort echo time sequences for the quantification of T<inf>1</inf>within phantom and human Achilles tendon at 3 T
Wright P., Jellus V., McGonagle D., Robson M., Ridgeway J., Hodgson R.
Ultrashort echo time (UTE) techniques enable direct imaging of musculoskeletal tissues with short T 2 allowing measurement of T 1 relaxation times. This article presents comparison of optimized 3D variable flip angle UTE (VFA-UTE) and 2D saturation recovery UTE (SR-UTE) sequences to quantify T 1 in agar phantoms and human Achilles tendon. Achilles tendon T 1 values for asymptomatic volunteers were compared to Achilles tendon T 1 values calculated from patients with clinical diagnoses of spondyloarthritis (SpA) and Achilles tendinopathy using an optimized VFA-UTE sequence. T 1 values from phantom data for VFA- and SR-UTE compare well against calculated T 1 values from an assumed gold standard inversion recovery spin echo sequence. Mean T 1 values in asymptomatic Achilles tendon were found to be 725 ± 42 ms and 698 ± 54 ms for SR- and VFA-UTE, respectively. The patient group mean T 1 value for Achilles tendon was found to be 957 ± 173 ms (P < 0.05) using an optimized VFA-UTE sequence with pulse repetition time of 6 ms and flip angles 4, 19, and 24°, taking a total 9 min acquisition time. The VFA-UTE technique appears clinically feasible for quantifying T 1 in Achilles tendon. T 1 measurements offer potential for detecting changes in Achilles tendon due to SpA without need for intravenous contrast agents. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc. Copyright © 2012 Wiley Periodicals, Inc.