title: Fast monitoring of T(1) , T(2) , and relative proton density (M(0) ) changes in skeletal muscles using an IR-TrueFISP sequence.
abstract: OBJECTIVE
  To investigate the feasibility of fast and simultaneous assessment of T(1) , T(2) , and M(0) (relative proton density) changes in skeletal muscle studies using an inversion recovery true fast imaging with steady-state precession (TrueFISP) sequence.
  
  
  METHODS
  NMR signal dynamics in calf muscles were analyzed under four different conditions: intravenous injection of a low-molecular weight Gd contrast agent (CA), postarterial occlusion reactive hyperemia, local cooling, and an exercise bout. Experiments were conducted on a clinical 3T whole-body scanner.
  
  
  RESULTS
  At rest, average muscle T(1) and T(2) values obtained from the IR-TrueFISP experiments were 1.34 ± 0.13 seconds and 45 ± 5 msec, respectively (median ± standard deviation). 1) Noticeable T(1) decreases (ΔT(1) max ≈-30%) were measured in the calf muscles after CA injection, while no significant changes were observed for T(2) and M(0) . 2) T(2) increased rapidly during reactive hyperemia and reached a peak value (+6%) at about 1 minute postischemia. During ischemia, a significant decrease was observed only in the soleus muscle. No significant paradigm-related changes in M(0) and T(1) were noted in all muscle groups, except in the m. soleus (ΔT(1) ≈+1% during reactive hyperemia). 3) Opposite variations in muscle T(1) (ΔT(1) max ≈-30%) and M(0) (ΔM(0) max ≈+25%) associated with local cooling were detected. 4) Concomitant changes in T(1) (ΔT(1) max ≈+15%), T(2) (ΔT(2) max ≈+35%), and M(0) (ΔM(0) max ≈+16%) were observed in the activated muscles following the exercise bout.
  
  
  CONCLUSIONS
  IR-TrueFISP was sufficiently fast and sensitive to detect small and transient T(1) , T(2) , and M(0) changes in the calf muscles under different experimental conditions. The sequence offers a time-resolution adequate to track rapid physiological adaptations in skeletal muscle.
authors: Institute of Myology, Paris, France. p.loureiro@institut-myologie.org
authors: Paulo Loureiro
authors: PL
authors: de Sousa
authors: Alexandre
authors: A
authors: Vignaud
authors: Servanne
authors: S
authors: Fleury
authors: Pierre G
authors: PG
authors: Carlier
mesh_terms: D003287:Contrast Media / Q000494:pharmacology; D003952:Diagnostic Imaging / Q000379:methods; D015444:Exercise; D005682:Gadolinium / Q000494:pharmacology; D006801:Humans; D006940:Hyperemia; D007275:Injections, Intravenous; D007511:Ischemia / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D015233:Models, Statistical; D018482:Muscle, Skeletal / Q000473:pathology*; D011522:Protons; D051598:Whole Body Imaging / Q000379:methods
chemical_list: D003287:Contrast Media; D011522:Protons; D005682:Gadolinium