T 1ρ relaxation and its application to MR histology

The application of T 1 P as an alternative contrast parameter in high‐field magnetic resonance histology (MRH) has been investigated. Spectroscopic measurements of T 1 P were performed on 5.75% agar and 1.0 mM MnCl 2 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 P relaxation times were calculated for the phantoms and muscle, diencephalon, and liver tissues. The 5.75% agar phantom and all tissues showed T 1 P dispersion with B 1 L , whereas the 1.0 mM MnCl 2 phantom showed no significant B 1 L dependence. T 1 P dispersion with B 0 was observed arising from the effects of diffusion through susceptibility‐induced gradients. T 1 P 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.