Simultaneous dynamic R2 R2', and R2* measurement using periodic π pulse shifting multiecho asymmetric spin echo sequence moving estimation strategy: A feasibility study for lower extremity muscle

Abstract

Purpose: The purpose of this study was to demonstrate the feasibility of simultaneous dynamic R2, R2, and R2* measurement of lower extremity muscle by means of a new method in which the periodic π pulse shifting multiecho asymmetric spin echo (psMASE) sequence is adopted together with a moving estimation (ME) strategy. Theory and Methods: The psMASE sequence is a modification of the multiecho asymmetric spin echo sequence determined by shifting the 180 ° refocusing pulse periodically. ME strategy is introduced to improve the temporal resolution of the simultaneous dynamic measurement of R2, R2, and R2*. Reproducibility measurements and comparison with reference methods were conducted. Furthermore, this method was tested on 10 healthy volunteers with the dynamic imaging of lower extremity muscles during a cuff occlusion release paradigm. Results: Both phantom and in vivo comparisons demonstrated that psMASE-ME–based R2 and R2* had good agreement with those calculated by multiecho spin echo and gradient echo sequences. Scan–rescan tests showed good reproducibility. Moreover, muscle R2, R2, and R2* increased obviously from rest to cuff occlusion and decreased significantly after cuff release. Conclusion: It is feasible to obtain high temporally resolved R2, R2, and R2* simultaneously with the proposed psMASE-ME method. Magn Reson Med 77:766–773, 2017. © 2016 International Society for Magnetic Resonance in Medicine.