Energy Delivery Direction Monitoring during Directional Catheter-based Ultrasound Thermal Ablation using Fitted
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Directional catheter-based ultrasound (CBUS) thermal ablation has the ability to enable precise spatial control of the ablation zone in deep-seated tumors by allowing angular modulation of targeted energy deposition. But this ability was limited due to lack of energy delivery monitoring method. Changes in ultrasound backscatter energy (CBE) imaging has the potential to be used to fill this gap due to its high sensitivity for monitoring the directional CBUS thermal ablation. However, this potential is limited by the edge outliers in CBE images and inescapable motion artifacts during tissue coagulation. Therefore, to address the above limitations, this study proposed the fitted motion-compensation CBE (fMoCo-CBE) imaging technique to monitor the energy delivery angles during the directional CBUS thermal ablation. The accuracy and feasibility of the proposed method were evaluated via ex vivo bovine livers and in vivo canine prostates' thermal ablation experiments. Compared with the energy delivery angles obtained without fitting and motion compensation, the angles monitored from the fMoCo-CBE images showed better agreement with the expected energy delivery directions. Specifically, fMoCo-CBEpos achieved the highest correlation coefficient with 0.920 ± 0.014 and the lowest estimation standard deviation with 32.56 ± 3.48°, indicating improved accuracy and stability in energy delivery direction monitoring. These results illustrated that the proposed method could estimate the energy delivery angles during directional CBUS thermal ablation and improve the estimation accuracy via fitting and motion correction significantly. The quantifications, tracking, and visualizations of energy delivery angles on the fMoCo-CBE images may provide useful feedback for future adjustment of the CBUS applicator and facilitate precision therapy during directional CBUS thermal ablation.
