Visualization of Tumor's vascularity for HIFU treatment with tissue motion correction

We developed a method for visualizing the vascularity of a tumor filled with contrast agents, which cannot be clearly seen in conventional harmonic images because of the low density of microbubble contrast agents. We investigated a time-averaging method by using multiple frames with tissue motion correction. For the measurement of tissue motion, we divide an image into extremely small regions so that the loss of correlation caused by tissue motion decreases. We applied the time-averaging method to both normal rabbit kidneys and tumor implanted in rabbit muscle. For the normal kidney, the renal vascularity, including the small vessels in the renal cortex, could be clearly seen without any motion artifacts, which cannot be seen in conventional images. For the tumor implanted in rabbit muscle, neovascularity could be seen more clearly than in conventional images. We also found that by averaging multiple frames of the moving tissue, speckles were reduced and static signals were enhanced, because the signals in the slice direction were compounded. With these results, we found that the time-averaging method is useful for detecting tumors in early stages, and allowing HIFU treatment to be performed accurately without damaging normal parts.