Characterization of T1rho sensitivity to metabolite and temperature changes

Spin-lattice relaxation in the rotating frame (T1ρ) is a relaxation parameter measured in nuclear magnetic resonance studies. This parameter has been found to be sensitive to chemical exchange processes occurring in diseased tissue associated with abnormal metabolism when measured in magnetic resonance imaging (MRI). Metabolic changes in tissue affected by abnormal metabolism can be quantified with good spatial and temporal resolution using T1ρ, better than a similar method of assessment known as CEST and current methods such as spectroscopic (¹H- and ³¹P-MRS) and nuclear medicine (PET) methods used in clinical settings. Though T1ρ has these advantages, there is no consensus as to which metabolic changes T1ρ is most sensitive. The metabolic changes may be pH related, or due to changes in concentration of metabolites like glucose and glycogen. This work is tries to identify which metabolite evokes the greatest change in T1ρ by studying the response of three spin relaxation measures (T1ρ, T2 and T1) at different temperatures. It was found that T1ρ is more sensitive to pH changes than glucose and lysine at 3T. Also at body temperature, the pH results showed an exponential decay trend for T1ρ signifying the limited range of sensitivity in the pH range of 6.9 to 7.5. The T2 results can be used to explain this trend.