Fast monitoring of T(1) , T(2) , and relative proton density (M(0) ) changes in skeletal muscles using an IR-TrueFISP sequence.

Purpose: 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. Materials and 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 6 standard deviation). 1) Noticeable T-1 decreases (Delta T-1 max approximate to-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 post-ischemia. 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 (Delta T-1 approximate to+1% during reactive hyperemia). 3) Opposite variations in muscle T-1 (Delta T-1 max approximate to-30%) and M-0 (Delta M-0 max approximate to+25%) associated with local cooling were detected. 4) Concomitant changes in T-1 (Delta T-1 max approximate to+15%), T-2 (Delta T-2 max approximate to+35%), and M-0 (Delta M-0 max approximate to+16%) were observed in the activated muscles following the exercise bout. Conclusion: 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.