In Vivo Thermal Ablation Monitoring Using Ultrasound Echo Decorrelation Imaging

Abstract

Previous work has shown ultrasound echo decorrelation imaging can track and quantify changes in echo signals to predict thermal damage during in vitro radiofrequency ablation (RFA). In the in vivo studies reported here, the feasibility of using echo decorrelation imaging as a treatment monitoring tool is assessed. RFA was performed on a normal swine liver (N = 5) and ultrasound ablation using image-ablate arrays was performed on a rabbit liver implanted with VX2 tumors (N = 2). Echo decorrelation and integrated backscatter were computed from Hilbert transformed pulse-echo data acquired during RFA and ultrasound ablation treatments. Receiver operating characteristic (ROC) curves were employed to assess the ability of echo decorrelation imaging and integrated backscatter to predict ablation. Area under the ROC curves (AUROC) was determined for RFA and ultrasound ablation using echo decorrelation imaging. Ablation was predicted more accurately using echo decorrelation imaging (AUROC 0.832 and 0.776 for RFA and ultrasound ablation respectively) than using integrated backscatter (AUROC 0.734 and 0.494).

Using Passive Cavitation Images to Classify High-Intensity Focused Ultrasound Lesions

“…The methodologies from Arvanitis and McDannold (2013) and Jensen et al (2013) are examples of how passive cavitation imaging can be used in conjunction with other techniques to predict HIFU lesion formation. Many other ultrasound imaging modalities have the potential to be used with passive cavitation imaging for monitoring lesion formation, speed-of-sound imaging, echo decorrelation imaging or elastography (Righetti et al, 1999; Anand and Kaczkowski, 2008; Liu and Ebbini, 2010; Choi et al, 2011; Bing et al, 2011; Subramanian et al 2014). …”

Echo Decorrelation Imaging of Rabbit Liver and VX2 Tumor during In Vivo Ultrasound Ablation

“…In-phase and quadrature echo signals were processed to construct B-mode images, as well as images of echo decorrelation and integrated backscatter, both as defined by Subramanian et al (2014). B-Mode images were constructed from logarithmically scaled envelopes (log| p ( r , t )|) of the IQ data and displayed using a 60-dB dynamic range.…”

“…The local instantaneous decorrelation term Δ( r , t ) defined by Subramanian et al (2014) was normalized by the inter-frame time to measure the decorrelation per millisecond. The local instantaneous decorrelation per millisecond was then ensemble-averaged over the group of 112 frames recorded after each therapy pulse to obtain a single decorrelation map for each cycle.…”

“…Echo decorrelation imaging, a pulse-echo method that maps heat-induced changes in ultrasound echoes over millisecond time scales, has exhibited promise for real-time monitoring of radiofrequency ablation (Mast et al 2008; Subramanian et al 2014), as well as ultrasound ablation using unfocused (Subramanian et al 2014) and focused (Kumon et al 2012; Matsuzawa et al 2012; Sasaki et al 2014) beams. However, the ability of echo decorrelation to predict the desired clinical end effect of thermal ablation ( i.e ., death of both malignant tumor tissue and a margin of normal liver tissue) has not been systematically investigated in vivo .…”

Thermometry and ablation monitoring with ultrasound

“…In another non-thermal strain technique that uses post-beamformed, I/Q data, Mast and colleagues at the University of Cincinnati have explored echo decorrelation imaging, which is dependent upon the formation of an integrated backscatter image (146). Echo decorrelation imaging is reported be more robust to tissue motion and bubble activity than thermal strain imaging, but at higher temperatures the images are qualitative, not quantitative.…”