Time-averaged high contrast ultrasound imaging with motion correction

We investigated a high-contrast ultrasound imaging method by averaging multiple frames with motion correction. The purpose of this study is to visualize the vascularity of peripheral vessels filled with contrast agents by using an averaging method which cannot be imaged clearly in conventional contrast image because of low density of the agent. To average signals from the same region of multiple frames accurately, tissue motion must be measured and corrected when averaging. Our approach for measurement is to divide an image into extremely small regions so that loss of correlation caused by tissue motion can be decreased. In vivo results on rabbit kidney revealed that the vascularity, including peripheral vessels, could be clearly imaged without any motion artifact by averaging 100 frames. Moreover, vessels that could not be imaged in the conventional contrast image were clearly imaged as a line structure, which was produced by a slight tissue motion in the slice direction. We also applied this time-averaging method to B-mode images of a human carotid artery. By averaging 30 frames, speckle signals were reduced and vessel, thyroid and the other structures were clearly imaged, because of compounding multiple frames obtained from various angles in the slice direction.