Proton T-1 rho-dispersion imaging of rodent brain at 1.9 T

Detection of (H2O)-O-17 with proton T-1p-dispersion imaging holds promise a s a means of quantifying metabolism and blood now with MRT. However, this t echnique requires a priori knowledge of the intrinsic T-1p dispersion of ti ssue. To investigate these properties, we implemented a T-1p imaging sequen ce on a 1.9-T Signs GE scanner. A series of T-1p images for different locki ng quencies and locking durations were obtained from rat brain in vivo and compared with 5 % (wt/vol) gelatin phantoms containing different concentrat ions of O-17 ranging from .037 % (natural abundance) to 2.0 atom %, Results revealed that, although there is considerable T-1p-dispersion in phantoms doped with (H2O)-O-17, the T-1p of rat brain undergoes minimal dispersion f or spin-locking frequencies between .2 and 1.5 kHz, A small degree of T dis persion is present below .2 kHz, which we postulate arises from natural-abu ndance (H2O)-O-17, Moreover, the signal-to-noise ratios of T-1p weighted im ages are significantly better than comparable Ta-weighted images, allowing for improved visualization of tissue contrast. We have also demonstrated th e feasibility of proton T-1p-dispersion imaging for detecting intravenous ( H2O)-O-17 on a live mouse brain. The potential application of this techniqu e to study brain perfusion is discussed.