Real-time control of radiofrequency ablation using three-dimensional ultrasound echo decorrelation imaging in normal and diseased ex vivo human liver

Ultrasound echo decorrelation imaging can successfully monitor and control thermal ablation of animal liver and tumor tissue ex vivo and in vivo. However, normal and diseased human liver has substantially different physical properties that affect echo decorrelation. Here, effects of human liver tissue condition on ablation guidance by three-dimensional echo decorrelation imaging are elucidated in experiments testing closed-loop control of radiofrequency ablation (RFA) in normal and diseased human liver tissue ex vivo. Approach: Samples of normal, steatotic, and cirrhotic human liver tissue underwent radiofrequency ablation (RFA), targeting a 20 mm-diameter spherical ablation zone. For each tissue condition, RFA was controlled by echo decorrelation in N > 14 trials, automatically ceasing if average cumulative decorrelation within the targeted ablation zone surpassed a predetermined threshold (successfully controlled trials), or otherwise completing a standard ablation cycle of the RFA generator (unsuccessfully controlled). For comparison, N = 14 RFA trials for each tissue condition followed the RFA generator's standard algorithm without echo decorrelation feedback (uncontrolled). Receiver operating characteristic (ROC) and precision-recall curve analyses compared 3D echo decorrelation maps to segmented ablation zones. To assess effects of closed-loop control and liver condition on treatment reliability, ablation volumes, rates, and Dice coefficients for measured vs. targeted ablation zones were statistically compared among control conditions and liver types. Results: ROC curves showed effective prediction of local ablation by echo decorrelation across all liver types and control conditions (0.876 ≤ AUROC ≤ 0.953). Successful control was significantly more frequent, ablated volumes were generally larger, and optimal echo decorrelation thresholds were smaller for normal compared to diseased liver. Significance: This study validates three-dimensional echo decorrelation imaging for monitoring and control of RFA in healthy and diseased human liver while elucidating the dependence of radiofrequency ablation and echo decorrelation outcomes on liver condition and resulting implications for clinical applications.