Tao Jin1, Seong-Gi Kim1
Department of Radiology,
The spin-lattice relaxation time in the rotating frame (T1rho) has been reported to be a sensitive indicator of cerebral ischemia and can provide complementary MR information of tissue status to water diffusion and perfusion. T1rho is most sensitive to molecular fluctuations with correlation time close to the inverse of the Rabi frequency of the applied spin-locking (SL) pulse. In biological tissue, previous studies have demonstrated that the chemical exchange between bulk water and labile protons of protein or metabolites is an important contributor for the T1rho relaxation in the frequency range of below several kHz. The chemical exchange contrast is related to the difference in the Larmor frequencies of the exchanging protons which increases with the magnetic field strength. Thus, to evaluate whether a large T1rho contrast can be detected at a high magnetic field of 9.4 T and to obtain some insight about the ischemia-induced changes in the tissue microenvironment, we studied the dynamic responses of T1rho during KCL-induced global ischemia for six different SL frequencies.