Ex vivo thermal ablation monitoring using three-dimensional ultrasound echo decorrelation imaging

Abstract

Echo decorrelation imaging is a method for quantitatively mapping transient heat-induced changes in pulse-echo ultrasound images. For clinical thermal ablation of liver cancer using radiofrequency or microwave ablation (RFA or MWA), real-time three-dimensional (3D) echo decorrelation imaging is necessary because the entire tumor, with typical diameter 2–5 cm, is ablated at once. We present a method for constructing 3D echo decorrelation maps during radiofrequency ablation (RFA) in ex vivo bovine liver using beamformed in-phase and quadrature (IQ) echo acquired from a Siemens Acuson SC2000 scanner and 4Z1c matrix array. To directly compare echo decorrelation images to the desired outcome of tissue ablation, 3D echo decorrelation images are compared to volumetric reconstructions of the thermal ablation zone, obtained from optical scans of regularly spaced tissue sections. Capability of echo decorrelation as a predictor of local ablation is assessed using receiver operator characteristic curve analysis. Similar to previous studies of two-dimensional echo decorrelation imaging, good correspondence is seen between 3D echo decorrelation images and ablated tissue histology.