In-Vivo Monitoring of Liver Regeneration by Ultrasound Localization Microscopy: A Feasibility Study

Liver regeneration is an important model of regenerative growth of tissues with an unclear mechanism. Monitoring the hemodynamic changes during liver regeneration may facilitate the understanding of the mechanism. Ultrasound localization microscopy (ULM) is an emerging technology that can visualize the microvascular structures and micro blood flow velocities with high spatial resolution, adequate penetration depth and wide imaging field of view, which is suitable for in-vivo monitoring of liver regeneration. We constructed a liver regeneration model in Sprague-Dawley (SD) rats with portal vein ligation (PVL) and monitored the hemodynamic changes in the right liver lobe with ULM. The 1 mm surroundings of the portal vein were selected as the region of interest (ROI). The velocity of the ROI is 15.17 ± 8.59 mm/s before PVL, 21.88 ± 10.49 mm/s 30 min after PVL, and 15.54 ± 9.64 mm/s 24 h after PVL. A further statistical analysis on the flow velocities in different ROIs and at different times indicated that the flow velocities of the portal vein and its branches rise 30 min after PVL and fell back 24 h after PVL. In conclusion, the feasibility of ULM in quantitative evaluation of liver regeneration by visualizing liver hemodynamics is demonstrated and the potential in understanding of the mechanism is promising.