T1ρ Dispersion profile of rat tissues in vitro at very low locking fields

The purpose of this study was to show the T1ρ dispersion profile in various rat tissues (liver, brain, spleen, kidney, heart and skeletal muscle) at low (0.1 T) B0 field at very low locking field B1, starting from 10 μT. The T1ρ dispersion profile showed a quite similar pattern in all tissues. The highest R1ρ relaxation rates were seen in the liver and muscle followed by the heart, whereas the values for spleen, kidney and brain were rather similar. The greatest difference between R2 relaxation rate and R1ρ relaxation rate at B1=10 μT was seen in the liver and muscle. The steepest slope for a dispersion curve was seen in the muscle. The value of T1ρ approximately approached the value of T2 when the locking field B1 approached 0. Except for the liver, the calculated apparent relaxation rate R2′ was slightly larger than the calculated one. The potential value of T1ρ imaging is to combine high R1 contrast of low-field imaging with the high signal-to-noise ratio (SNR) of high static field imaging. T1ρ relaxation and dispersion data presented in the current study help to optimize the rotating-frame MR imaging.