T-1 rho relaxation and its application to MR histology

The application of T-1 rho as an alternative contrast parameter in high-field magnetic resonance histology (MRH) has been investigated. Spectroscopic measurements of T-1 rho were performed on 5.75% agar and 1,0 mM MnCl2 phantoms at 9.4 T to validate the accuracy of the imaging measurements. Image studies were performed at 2.0 and 9.4 T on perfusion-fixed 17.5-day-old mouse embryos, T-1, T-2, and T-1 rho relaxation times were calculated for the phantoms and muscle, diencephalon, and liver tissues. The 5.75% agar phantom and all tissues showed T-1 rho dispersion with B-1L, whereas the 1.0 mM MnCl2 phantom showed no significant B-1L dependence. T-1 rho dispersion with B-0 was observed arising from the effects of diffusion through susceptibility-induced gradients. T-1 rho shows promise as a contrast parameter in high-field MRH because it is capable of producing T-2-like contrast without the susceptibility artifacts associated with T-2-weighted images.