In vivo thermal ablation control using three-dimensional echo decorrelation imaging in swine liver

Abstract

In experiments modeling clinical thermal ablation of liver tumors, radiofrequency ablation (RFA) of swine liver was controlled using a three-dimensional (3D) ultrasound echo decorrelation imaging. Up to six ablations with target diameter 2 cm were done in each animal’s liver using a clinical RFA system (RITA/Angiodynamics, 50 W, 6–10 min). Paired sequential volumes of beamformed pulse-echo data (inter-frame time <50 ms) were acquired from a Siemens Acuson SC2000 scanner with a Z6Ms transesophageal matrix array and transferred via an Ethernet to a computer running a custom MATLAB program to compute 3D echo decorrelation images. When the average cumulative, motion-compensated echo decorrelation within the planned ablation zone exceeded a prespecified threshold determined from preliminary trials, ablation was ceased automatically. After each procedure, the animal’s liver was excised, uniformly sectioned, and optically scanned to reconstruct 3D ablation zones. Local ablation prediction was assessed using receiver operating characteristic (ROC) curve analysis comparing echo decorrelation images to co-registered ablation zones. To assess differences in outcomes, ablation zone volumes, ablation rates, Dice coefficients for measured versus targeted ablation zones, and ROC curves were statistically compared for controlled versus uncontrolled trials. The results indicate promise for control of in vivo thermal ablation using motion-corrected 3D echo decorrelation imaging.