Black blood T1rho MR imaging may diagnose early stage liver fibrosis: a proof-of-principle study with rat biliary duct ligation model

Background: To explore black blood T1rho (T1 rho) liver imaging and investigate the earliest stage when biliary duct ligation (BDL) induced liver fibrosis can be diagnosed. Methods: MR was performed at 3 Tesla. A T1 rho prepared 2D fast spin echo (FSE) sequence with acquisition of four spin lock times (TSLs: 1, 10, 30, and 50 msec) and spin-lock frequency of 500 Hz was applied. Inherent black blood effect of FSE and double inversion recovery (DIR) achieved blood signal suppression, and 3 axial sections per liver were obtained. Male Sprague-Dawley rats were scanned at baseline (n=32), and on day-3 (n=13), day-5 (n=11), day-7 (n=10), day-10 (n=4) respectively after BDL. Hematoxylin-eosin (HE) and picrosirius red staining liver histology was obtained at these time points. Results: The physiological liver parenchyma T1 rho was 38.38+/-1.53 msec (range, 36.05-41.53 msec). Liver T1 rho value elevated progressively after BDL. On day-10 after BDL all experimental animals can be separated from normal liver based on T1 rho measurement with lowest value being 42.82 msec. Day-7 and day-10 liver resembled METAVIR stage-F1/F2 fibrosis, and fibrous area counted for 0.22%+/-0.13% and 0.38%+/-0.44% of liver parenchyma area, respectively. Conclusions: This study provides the first proof-of-principle that T1 rho might diagnose early stage liver fibrosis.