Fast measurement of the quadriceps femoris muscle transverse relaxation time at high magnetic field using segmented echo-planar imaging

Abstract : PURPOSE: To assess and validate a technique for transverse relaxation time (T2 ) measurements of resting and recovering skeletal muscle following exercise with a high temporal resolution and large volume coverage using segmented spin-echo echo-planar imaging (sSE-EPI). MATERIALS AND METHODS: Experiments were performed on a 3T magnetic resonance imaging (MRI) scanner using a multislice sSE-EPI technique applied at different echo times (TEs). T2 measurements were first validated in vitro in calibrated T2 phantoms (range: 25-152 ms) by comparing sSE-EPI, standard spin-echo (SE), and multislice multiecho (MSME) techniques (using a fitting procedure or a 2-TEs calculation). In vivo measurements of resting T2 quadriceps femoris (QF) muscle were performed with both sSE-EPI and MSME sequences. Finally, sSE-EPI was used to quantify T2 changes in recovering muscle after an exercise. RESULTS: T2 values measured in vitro with sSE-EPI were similar to those assessed with SE (P \textgreater 0.05). In vitro and in vivo T2 measurements obtained with sSE-EPI were independent of the T2 determination procedure (P \textgreater 0.05). In contrast, both in vitro and in vivo T2 values derived from MSME were significantly different when using 2-TEs calculation as compared to the fitting procedure (P \textless 0.05). sSE-EPI allowed the detection of increased T2 values in the QF muscle immediately after exercise (+14 ± 9%), while lower T2 values were recorded less than 2 min afterwards (P \textless 0.05). CONCLUSION: sSE-EPI sequence is a relevant method to monitor exercise-induced T2 changes of skeletal muscles over large volume coverage and to detect abnormal patterns of muscle activation. J. Magn. Reson. Imaging 2016.