T1 rho relaxation and its application to MR histology

The application of T1 rho an an alternative contrast parameter in high-field magnetic resonance histology (MRH) has been investigated. Spectroscopic measurements of T1 rho were performed on 5.75% agar and 1.0 mM MnCI2 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. T1, T2, and T1 rho relaxation times were calculated for the phantoms and muscle, diencephalon, and liver tissues. The 5.75% agar phantom and all tissues showed T1 rho dispersion with B1L, whereas the 1.0 mM MnCI2 phantom showed no significant B1L dependence. T1 rho dispersion with B(O) was observed arising from the effects of diffusion through susceptibility-induced gradients. T1 rho shows promise as a contrast parameter in high-field MRH because it is capable of producing T2-like contrast without the susceptibility artifacts associated with T2-weighted images.