Objectives: Recently it was shown that the magnetic resonance imaging (MRI) T1ρ value increased with the severity of liver fibrosis in rats with bile duct ligation. Using a rat carbon tetrachloride (CCl(4)) liver injury model, this study further investigated the merit of T1ρ relaxation for liver fibrosis evaluation.
Methods: Male Sprague-Dawley rats received intraperitoneal injection of 2 ml/kg CCl(4) twice weekly for up to 6 weeks. Then CCl(4) was withdrawn and the animals were allowed to recover. Liver T1ρ 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 CCl(4) injection, and they were also examined at 1 week and 4 weeks post CCl(4) withdrawal. Liver histology was also sampled at these time points.
Results: Liver T1ρ values increased slightly, though significantly, on day 2, and then increased further and were highest at week 6 post CCl(4) insults. The relative liver signal intensity change on T2-weighted images followed a different time course compared with that of T1ρ. Liver T1ρ values decreased upon the withdrawal of the CCl(4) insult. Histology confirmed the animals had typical CCl(4) liver injury and fibrosis progression and regression processes.
Conclusions: MR T1ρ imaging can monitor CCl(4)-induced liver injury and fibrosis.
Key points: • MR T1ρ is a valuable imaging biomarker for liver injury/fibrosis. • Liver T1ρ was only mildly affected by oedema and acute inflammation. • Liver MR T1ρ decreased when liver fibrosis and injury regressed.