Role of contrast-enhanced ultrasound (CEUS) in evaluation of thermal ablation zone

Thermal ablation has emerged as a mainstay therapy for primary and metastatic liver malignancy. Percutaneous thermal ablation is usually performed under CT and/or ultrasound guidance. CT guidance frequently utilizes iodinated contrast for tumor targeting, with additional radiation and contrast required at the end of the procedure to ensure satisfactory ablation margins. Contrast-enhanced ultrasound (CEUS) is an imaging technique utilizing microbubble contrast agents to demonstrate blood flow and tissue perfusion. In this study, we performed a retrospective review to assess the utility of CEUS in the immediate post ablation detection of residual tumor.

Sixty-four ablations were retrospectively reviewed. 6/64 ablations (9.4%) had residual tumor on the first follow-up imaging after thermal ablation. There were two groups of patients. Group 1 underwent standard protocol thermal ablation with CT and/or ultrasound guidance. Group 2 not only had thermal ablation with a protocol identical to group 1, but also had CEUS assessment at the conclusion of the procedure to ensure satisfactory ablation zone.

The residual tumor rate in group 1 was 16.7% and the residual tumor rate in group 2 was 0%. The difference between the groups was statistically significant with a p value of 0.023. The results suggest that using CEUS assessment immediately after the ablation procedure reduces the rate of residual tumor after thermal ablation.

CEUS evaluation at the end of an ablation procedure is a powerful technique providing critical information to the treating interventional radiologist, without additional nephrotoxic contrast or ionizing radiation.