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

To compare mono- and bi-exponential relaxation model equations to discriminate between normal and fatty liver disease.

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 T₂ maps were generated using mono-exponential decay function to calculate T_2M , and a bi-exponential to calculate, short T₂ component (T_2S ), long T₂ 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.

F-test and AIC showed that in the CDAA group, T₂ bi-exponential model described the signal of T₂ 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.

In the fatty liver of CDAA rats we have shown that T₂ weighted images fit the bi-exponential model better than mono-exponential decays thus providing a better description of the data.

1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:468-476.