MR T1ρ as an imaging biomarker for monitoring liver injury progression and regression: an experimental study in rats with carbon tetrachloride intoxication

Recently it was shown that the magnetic resonance imaging (MRI) T1 rho value increased with the severity of liver fibrosis in rats with bile duct ligation. Using a rat carbon tetrachloride (CCl4) liver injury model, this study further investigated the merit of T1 rho relaxation for liver fibrosis evaluation. Male Sprague-Dawley rats received intraperitoneal injection of 2 ml/kg CCl4 twice weekly for up to 6 weeks. Then CCl4 was withdrawn and the animals were allowed to recover. Liver T1 rho MRI and conventional T2-weighted images were acquired. Animals underwent MRI at baseline and at 2 days, 2 weeks, 4 weeks and 6 weeks post CCl4 injection, and they were also examined at 1 week and 4 weeks post CCl4 withdrawal. Liver histology was also sampled at these time points. Liver T1 rho values increased slightly, though significantly, on day 2, and then increased further and were highest at week 6 post CCl4 insults. The relative liver signal intensity change on T2-weighted images followed a different time course compared with that of T1 rho. Liver T1 rho values decreased upon the withdrawal of the CCl4 insult. Histology confirmed the animals had typical CCl4 liver injury and fibrosis progression and regression processes. MR T1 rho imaging can monitor CCl4-induced liver injury and fibrosis. aEuro cent MR T1 rho is a valuable imaging biomarker for liver injury/fibrosis. aEuro cent Liver T1 rho was only mildly affected by oedema and acute inflammation. aEuro cent Liver MR T1 rho decreased when liver fibrosis and injury regressed.