Nuclear magnetic resonance spectroscopy and imaging in the study of experimental liver diseases

We are investigating potential noninvasive new strategies for the assessment of liver injury, steatosis, and hepatic tumor development. These techniques employ nuclear magnetic resonance (NMR) imaging and spectroscopy. Accordingly, several experimental animal models of liver injury and steatosis produced in rats by ethanol, azaserine, L-ethionine, carbon tetrachloride, and D-galactosamine. Ethanol and L-ethionine induce acute steatosis without necrosis, whereas azaserine, carbon tetrachloride, and D-galactosamine are known to produce steatosis with varying degrees of hepatic necrosis. Triglyceride content and protein spin relaxation times were measured. T1 values were analyzed by using an inversion recovery technique at eight different tau values (20 msec to 2.50 sec) and T2 by Carr-Purcell-Meibloom-Gill pulse sequences with 10 spin echoes (4-40 msec). We also performed NMR imaging studies on controls and ethanol-induced steatosis using a 60-MHz Technicare 8-cm bore superconducting system. Results of these experiments indicate that varying degrees of steatosis produce striking changes in T2 without inducing changes in T1, whereas necrosis superimposed on steatosis produces T1 changes as well. Thus, these NMR spectroscopy and imaging studies demonstrated that steatosis may be clearly defined in vitro and in vivo.