Quantitative measurement of creatine content in skeletal muscle using 1H-MRS

Magnetic resonance spectroscopy (MRS) is used for non-invasively investigating metabolism and concentration of biomolecules in skeletal muscles and other tissues. MRS has a potential to become a tool for clinical diagnosis and for predicting disease prognosis. In this study, the ¹H spectra of skeletal muscles with and without atrophy were obtained and a quantitative evaluation of the content of creatine in the muscles was performed. The left sciatic nerves of nine week old rats were transected and at 2 and 4 weeks after the surgery, ¹H spectra of the muscles were obtained. Spectra of 11 and 13 weeks old normal rats were also obtained for controls. Water spectra were acquired from a 2×2×2 mm³ voxel located on the left gastrocnemius muscle. The signal intensities and the relaxation times of water and creatine were then estimated. Results show that the prolongation of the T₁ relaxation times of water in the denervated muscle is attributable to a decrease in the muscle water content and an increase in the extracellular fluid space. Creatine is involved with the reaction for producing adenosine triphosphate, the essential energy source for muscular contraction. The quantification of creatine may prove useful in evaluating atrophy and recovery process of muscles.