In vivo proton magnetic resonance spectroscopy of liver metabolites in non-alcoholic fatty liver disease in rats: T2 relaxation times in methylene protons

• Relaxation time could be useful for quantitative characterization of liver disease.
• Relaxation reflecting J-coupling effect will improve quantification of metabolite.
• 1H-MRS allows sufficient spectral resolution and SNR for lipid resonances.

The aim of this study was to evaluate the transverse relaxation time of methylene resonance as compared to other lipid resonances. The examinations were performed using a 3.0 T scanner with a point-resolved spectroscopy (PRESS) sequence. Lipid relaxation time in a lipid phantom filled with canola oil was estimated with a repetition time (TR) of 6000 ms and echo time (TE) of 40–550 ms. For in vivo proton magnetic resonance spectroscopy (1H-MRS), eight male Sprague–Dawley rats were given free access to a normal-chow (NC) and another eight male Sprague–Dawley rats were given free access to a high-fat (HF) diet. Both groups drank water ad libitum. T2 measurements in the rats’ livers were conducted at a fixed TR of 6000 ms and TE of 40–220 ms. Exponential curve fitting quality was calculated through the coefficients of determination (R2). Chemical analyses of the phantom and livers were not performed, but T2 decay curves were acquired. The T2 relaxation time of methylene resonance was estimated as follows: NC rats, 37.1 ± 4.3 ms; HF rats, 31.4 ± 1.8 ms (p < 0.05). The extrapolated M0 values were higher in HF rats than in NC rats (p < 0.005). This study of 1H MRS led to sufficient spectral resolution and signal-to-noise ratio differences to characterize the T2 relaxation times of methylene resonance. 1H MRS relaxation times may be useful for quantitative characterization of various liver diseases, including fatty liver disease.