A novel method for monitoring liver ablation using ultrasound elastography

Monitoring the ablation process in order to document the adequacy of margins during treatment is of significant importance. Observing that the ablation lesion is harder than normal tissue, it has been proposed to monitor the ablation using ultrasound elastography. Furthermore, it has been reported that the ablated cancer tumor is harder than ablated normal tissue. In this paper we propose an ultrasound elastography technique for visualizing the ablation lesion and the ablated cancerous tumor in Hepatocellular carcinoma (HCC). This work focuses on devising techniques to generate elasticity images which distinguish the ablated cancerous tumor and the ablated normal lesion. We first calculate the displacement field between two ultrasound images acquired before and after some compression. We then use the displacement field to calculate the correlation coefficient between the two images. Parts of the tissue that undergo large deformation give small correlation coefficient due to decorrelation within each window, and parts of the tissue that undergo small deformation give large correlation coefficient. Simulating phantoms with two lesions, a harder tumor inside a hard lesion, using finite element and Field II, we show that this method enables delineating the tumor from the lesion.