Non-rigid Motion Correction for Ultrasound Localization Microscopy of the Liver in vivo

Chronic liver diseases (CLDs) are a major killer of humans, and more than 1 billion people suffer from CLDs worldwide, which are likely to develop significant liver fibrosis (LF) and even cirrhosis. However, current noninvasive diagnostic methods for liver diseases are insensitive to early lesions, so accurate assessment of LF at early stage is very important for the treatment arrangement and fibrosis reversal before cirrhosis. Ultrasound localization microscopy (ULM) with contrast microbubbles (MBs) have been proposed by several groups and may have potential in evaluating LF at early stage. Unfortunately, breathing and heart beating can introduce motion artifacts in liver ULM, which brings the challenge for LF evaluation with ULM. Recently, rigid motion correction (MoCo) has been proposed to improve the performance of ULM of the brain and kidney. Considering typical non-rigid motion in the liver, the performance of rigid MoCo may be limited. Therefore, we propose a non-rigid MoCo method based on speckle tracking to improve the performance of liver ULM more effectively. Results of in vivo experiments indicate that ULM with non-rigid MoCo obtains better resolution and more continuous microvessels (MVs) than rigid MoCo.