1Biomedical and Metabolic Imaging Branch, NIH/NIDDK, Bethesda, MD, United States
Single volume 1H-MRS can be used to measure human liver glycogen in vivo, but various factors could lead to quantitation errors. T1 and T2 relaxation effects were examined on glycogen phantoms with ionic strength, pH and temperature mimicking the intracellular environment of the liver using the same PRESS sequence and parameters used for in-vivo measurements of glycogen in humans. Signal variations as a function of echo time (TE) and echo spacing with a fixed TE showed effects of homonuclear coupling. Thus, assuming an exponential model to correct glycogen signals for relaxation could lead to an underestimation of the glycogen concentrations.