Dynamic Changes in the Tissue Microenvironment Induced by Hypercapnia & Hyperoxia: A T1rho Dispersion Study at 9.4T

Tao Jin¹, Seong-Gi Kim¹

The spin-lattice relaxation time in the rotating frame (T1rho) has been applied in many pathological studies, including cartilage degradation, cerebral ischemia, and neurodegeneration diseases. Recently, it has also been reported that the T1rho contrast can detect dynamic changes in the tissue microenvironment induced by hypercapnia, hyperoxia challenges, or neuronal activation. T1rho is most sensitive to molecular fluctuations with correlation times close to the inverse of Rabi frequency of the applied spin-locking (SL) pulse. Thus, the T1rho relaxation time, measured with different SL frequencies, which is termed T1rho dispersion, provides valuable information about the underlying physiological mechanisms. Previous studies have demonstrated that the chemical exchange between labile protons of proteins and the bulk water may be an important contributor to T1rho dispersion in biological tissues in the low-frequency range of below several kHz. In order to gain more insight about the underlying mechanisms of dynamic T1rho changes, we investigated the T1rho response during hypercapnia and hyperoxia for two different SL frequencies.