T1p MR imaging characteristics of human anterior tibial and gastrocnemius muscles

Rationale and Objectives. The authors evaluated the value of T1 rho in relation to T1 and T2 in the characterization of human muscles. Materials and Methods. The authors studied the effect of muscle type (anterior tibial [AT] and gastrocnemius [GC]), sex, and age on 1/T1 and 1/T2 at 0.1 T and 1/T1 rho at locking-field B(1)s (spin-locking radio-frequency magnetic induction field) of 10-160 mu T in 38 healthy volunteers. The contrast-to-noise ratio (CNR) between muscle and fat was evaluated with different T1-, T2-, and T1 rho-weighted magnetic resonance (MR) sequences. Results. The 1/T1, 1/T2, and 1/T1 rho were slightly higher in AT than in GC muscles. The 1/T2 and 1/T1 rho of AT muscles showed a sex dependence, whereas no correlation with age was found. The CNR of the T1 rho-weighted images did not markedly differ from that of the T1- and T2-weighted images. Conclusion. T1 rho is as sensitive as T2 to the composition of muscle, whereas T1 is less sensitive. In MR imaging of normal muscle, T1 rho and T2 provide a relatively similar tissue contrast.