Magnetic resonance spin–spin relaxation time estimation in a rat model of fatty liver disease

Purpose To compare mono‐ and bi‐exponential relaxation model equations to discriminate between normal and fatty liver disease. Materials and Methods Six rats on a choline deficient amino acid modified (CDAA) diet and six on normal chow were studied. Multiple spin echo images with increasing echo times (TEs) were collected at 9.4T. Pixel‐wise T 2 maps were generated using mono‐exponential decay function to calculate T 2M , and a bi‐exponential to calculate, short T 2 component (T 2S ), long T 2 component (T 2L ), and fractions of these components ( ρ S , ρ L ), respectively. Statistical F‐tests and Akaike's information criterion (AIC) were used to assess the relative performance of the two models. Results F‐test and AIC showed that in the CDAA group, T 2 bi‐exponential model described the signal of T 2 weighted imaging of the liver better than the mono‐exponential model. Controls were best described by the mono‐exponential model. Mean values for T 2M , T 2L , T 2S , ρ S , ρ L were 31.2 ± 0.7 ms, 72.8 ± 3.3 ms, 8.2 ± 0.6 ms,71.2 ± 2.1%, 30.4 ± 1.3%, respectively, in CDAA rats, compared with 18.8 ± 0.5 ms, 32.3 ± 0.7 ms, 9.2 ± 1.8 ms, 79 ± 2%, 21.0 ± 1.1% in controls. Conclusion In the fatty liver of CDAA rats we have shown that T 2 weighted images fit the bi‐exponential model better than mono‐exponential decays thus providing a better description of the data. Level of Evidence: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:468–476.