Echo Decorrelation Imaging Research Articles

Monitoring radiofrequency ablation in ex vivo human liver using 3D echo decorrelation imaging augmented by deep learning

Monitoring of radiofrequency ablation (RFA) is desirable to improve safety and efficacy of liver tumor treatment. Three-dimensional ultrasound echo decorrelation imaging can successfully predict local ablation effects but has had limited success in mapping ablation zone margins and local tissue temperature. Here, a supervised deep learning approach is investigated to improve prediction of ablation zones and tissue temperature from 3D echo decorrelation images. RFA was performed on ex vivo human liver tissue, including normal, fibrotic, and cirrhotic liver (N > 30). During ablation, pairs of echo volumes were acquired with a 4.5 MHz transesophageal matrix array, 3D echo decorrelation images were computed for each volume pair, and temperatures measured by fourthermocouples integrated into the RFA probe were recorded. Tissue was then frozen, sectioned, scanned, and ablation zones were manually segmented. For prediction of ablation zones, B-mode and echo decorrelation images were input to a U-net convolutional neural network to segment ablation margins, with histology serving as ground truth for training and cross-validation. For prediction of temperature, echo decorrelation values at the thermocouple locations were used as input to train a dense network, minimizing mean-squared-error versus measured temperatures. The results indicate promise for improved mapping of tissue ablation and temperature.

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

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.

Three-dimensional echo decorrelation monitoring of radiofrequency ablation in ex vivo bovine liver.

Three-dimensional (3D) echo decorrelation imaging was investigated for monitoring radiofrequency ablation (RFA) in ex vivo bovine liver. RFA experiments (N = 14) were imaged by 3D ultrasound using a matrix array, with in-phase and quadrature complex echo volumes acquired about every 11 s. Tissue specimens were then frozen at -80 °C, sectioned, and semi-automatically segmented. Receiver operating characteristic (ROC) curves were constructed for assessing ablation prediction performance of 3D echo decorrelation with three potential normalization approaches, as well as 3D integrated backscatter (IBS). ROC analysis indicated that 3D echo decorrelation imaging is potentially a good predictor of local RFA, with the best prediction performance observed for globally normalized decorrelation. Tissue temperatures, recorded by four thermocouples integrated into the RFA probe, showed good correspondence with spatially averaged decorrelation and statistically significant but weak correlation with measured echo decorrelation at the same spatial locations. In tests predicting ablation zones using a weighted K-means clustering approach, echo decorrelation performed better than IBS, with smaller root mean square volume errors and higher Dice coefficients relative to measured ablation zones. These results suggest that 3D echo decorrelation and IBS imaging are capable of real-time monitoring of thermal ablation, with potential application to clinical treatment of liver tumors.

Motion-corrected echo decorrelation imaging for monitoring exvivo cardiac ablation

Radiofrequency ablation for treatment of cardiac arrhythmia would benefit from real-time monitoring of ablation progress. Echo decorrelation imaging has been shown to predict local ablation but is susceptible to artifacts caused by heart motion. Here, a method for motion-corrected echo decorrelation imaging is tested in ex vivo ablation of bovine cardiac muscle with controlled motion. Experiments employed a Stockert 70 generator and a 4-mm Celsius catheter (Biosense Webster) with the ablation duration of 3min at the target ablation temperature of 90 °C, resulting in thermal lesions of diameter about 1 cm. Cyclical motion was induced by a stepping motor system (Velmex) with velocities of 0–10 mm/s in the travel range of 1.5 cm. Pulse-echo ultrasound images were acquired by an Acuson SC2000 scanner with a Z6Ms transesophageal matrix array (Siemens). Throughout ablation at intervals of 5–6 s, sequentially paired bi-plane images were acquired as complex (IQ) beamformed echoes with an interframe time of 9–13 ms. Regions of interest (ROIs), one including the catheter location and one outside the ablation zone, were tracked using detection of the myocardial wall boundary and spatial cross-correlation. Echo decorrelation within the ablation ROI was then mapped and compensated to remove motion-induced decorrelation measured in the reference ROI. Receiver operating characteristic curves characterize accuracy for predictions of local myocardial ablation by motion-compensated echo decorrelation imaging as a function of the induced motion amplitude.

Three-dimensional echo decorrelation imaging of percutaneous microwave ablation in liver tumors

In a pilot clinical study, patients underwent standard-of-care percutaneous microwave ablation (MWA) of liver tumors with monitoring by three-dimensional (3D) ultrasound echo decorrelation imaging. An MWA needle (Amica) was inserted into each tumor, guided by x-ray computed tomography (CT) and ultrasound imaging. A matrix ultrasound array (4Z1c array with Acuson SC2000 scanner, Siemens) was positioned on patients’ skin near the MWA needle insertion point. Paired sequential complex in-phase/quadrature (IQ) echo volumes (inter-frame time 5–20 ms) were acquired throughout ablation at 10–20 s intervals, then processed to form 3D echo decorrelation images. Respiratory motion was estimated and compensated using a theoretical model that separates motion- and heat-induced echo decorrelation. Volumetric B-mode images constructed from the same IQ data were rigidly registered to follow-up contrast-enhanced magnetic resonance (MR) image volumes, recorded within 4 days after MWA. Specified registration transformations were then applied to cumulative 3D echo decorrelation maps, which were compared voxel-wise to ablation zones segmented from MR images. Receiver operator characteristic (ROC) curve analysis indicated effective prediction of local ablation by motion-compensated echo decorrelation imaging. Comparison with subsequent follow-up MR images tested the ability of 3D echo decorrelation imaging to predict any incomplete treatment or recurrence of treated tumors.

Monitoring microwave ablation using ultrasound homodyned K imaging based on the noise-assisted correlation algorithm: An ex vivo study

In this paper, we proposed ultrasound homodyned K (HK) imaging based on the noise-assisted correlation algorithm (NCA) for monitoring microwave ablation of porcine liver ex vivo. The NCA-based HK (αNCA and kNCA) imaging was compared with NCA-based Nakagami (mNCA) imaging and NCA-based cumulative echo decorrelation (CEDNCA) imaging. Backscattered ultrasound radiofrequency signals of porcine liver ex vivo during and after the heating of microwave ablation were collected (n = 15), which were processed for constructing B-mode imaging, NCA-based HK imaging, NCA-based Nakagami imaging, and NCA-based CED imaging. To quantitatively evaluate the final coagulation zone, the polynomial approximation (PAX) technique was applied. The accuracy of detecting coagulation area with αNCA, kNCA, mNCA, and CEDNCA parametric imaging was evaluated by comparing the PAX imaging with the gross pathology. The receiver operating characteristic (ROC) curve was used to further evaluate the performance of the three quantitative ultrasound imaging methods for detecting the coagulation zone. Experimental results showed that the average accuracies of αNCA, kNCA, mNCA, and CEDNCA parametric imaging combined with PAX imaging were 89.6%, 83.25%, 89.23%, and 91.6%, respectively. The average areas under the ROC curve (AUROCs) of αNCA, kNCA, mNCA, and CEDNCA parametric imaging were 0.83, 0.77, 0.83, and 0.86, respectively. The proposed NCA-based HK imaging may be used as a new method for monitoring microwave ablation.

Analysis of three-dimensional echo decorrelation and integrated backscatter imaging during ex vivo radiofrequency ablation

Radiofrequency ablation experiments were performed in ex vivo bovine liver (N = 14) using a clinical ablation system (RITA 1500X generator and StarBurst probe, Angiodynamics). Three-dimensional (3-D) ultrasound images were acquired as complex beamformed echo volumes from a Siemens Acuson SC2000 scanner with a 4Z1c matrix array. Echo decorrelation images, depicting echo changes between sequential volumes (interframe time 18 ms), and integrated backscatter (IBS) images, depicting local changes in echogenicity relative to baseline, were computed in 3-D at 11 s intervals throughout each treatment. To assess potential for real-time prediction of tissue ablation, cumulative 3-D echo decorrelation and integrated backscatter images were compared to reconstructed ablation zones, segmented from optically scanned tissue sections. Both echo decorrelation and IBS provided good prediction of local ablation using receiver operator characteristic (ROC) curve analysis (area under curve 0.91 for echo decorrelation normalized to global echo energy; >0.85 for all parameters), with accuracy depending weakly on correlation window size. While ablation regions were predicted fairly well (Dice coefficients >0.6), ablation zone volume was not consistently predicted by thresholded parameter maps. Both echo decorrelation and IBS showed weak but statistically significant correlation with simultaneous, co-located tissue temperatures measured by four thermocouples on the RF probe.

Real-time control of radiofrequency ablation by three-dimensional echo decorrelation imaging

Feasibility for real-time control of radiofrequency ablation (RFA) by three-dimensional (3-D) echo decorrelation imaging, with potential application to liver cancer treatment, is investigated. Ex vivo bovine liver is treated using a clinical RFA system (RITA 1500X generator with StarBurst probe, Angiodynamics). During ablation, pairs of echo volumes from a Siemens SC2000 scanner with a 4Z1c matrix array probe (inter-frame time 18 ms) are recorded as in-phase and quadrature (IQ) data. 3-D echo decorrelation maps are computed from these volume pairs every 11 s. Cumulative echo decorrelation, defined as the temporal maximum decorrelation for each voxel, is spatially averaged within a spherical region of interest (ROI) centered at the RF needle tip. Once the spatially averaged cumulative decorrelation within the spherical ROI exceeds a predefined threshold, ablation is halted by communication with the RF generator via a pneumatic switch connected to a microcontroller circuit. The control threshold and ROI were determined by empirically evaluating predictive performance of decorrelation in preliminary uncontrolled ablation trials. Controlled and uncontrolled ablation are compared based on correspondence of sectioned tissue histology to targeted ablation zones, receiver operating characteristic curve analysis of local ablation prediction by echo decorrelation, treatment duration, and ablation rate.

Numerical analysis of three-dimensional echo decorrelation imaging.

A numerical model for three-dimensional echo decorrelation imaging, a pulse-echo ultrasound method applicable to thermal ablation monitoring, is presented. Beam patterns for steered transmit and receive array apertures are combined with a three-dimensional numerical tissue model to yield beamformed scan lines in a pyramidal configuration, volumetric B-mode images, and spatial maps of normalized decorrelation between sequential image volumes. Simulated three-dimensional echo decorrelation images of random media are analyzed as estimators of local tissue reflectivity decoherence, mimicking thermal ablation effects. The estimation error is analyzed as a function of correlation window size, scan line density, and ensemble averaging of decorrelation maps.

In vivo ultrasound thermal ablation control using echo decorrelation imaging in rabbit liver and VX2 tumor.

The utility of echo decorrelation imaging feedback for real-time control of in vivo ultrasound thermal ablation was assessed in rabbit liver with VX2 tumor. High-intensity focused ultrasound (HIFU) and unfocused (bulk) ablation were performed using 5 MHz linear image-ablate arrays. Treatments comprised up to nine lower-power sonications, followed by up to nine higher-power sonications, ceasing when the average cumulative echo decorrelation within a control region of interest exceeded a predefined threshold (− 2.3, log10-scaled echo decorrelation per millisecond, corresponding to 90% specificity for tumor ablation prediction in previous in vivo experiments). This threshold was exceeded in all cases for both HIFU (N = 12) and bulk (N = 8) ablation. Controlled HIFU trials achieved a significantly higher average ablation rate compared to comparable ablation trials without image-based control, reported previously. Both controlled HIFU and bulk ablation trials required significantly less treatment time than these previous uncontrolled trials. Prediction of local liver and VX2 tumor ablation using echo decorrelation was tested using receiver operator characteristic curve analysis, showing prediction capability statistically equivalent to uncontrolled trials. Compared to uncontrolled trials, controlled trials resulted in smaller thermal ablation regions and higher contrast between echo decorrelation in treated vs. untreated regions. These results indicate that control using echo decorrelation imaging may reduce treatment duration and increase treatment reliability for in vivo thermal ablation.

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

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.

Biomedical acoustics research at the Image-Guided Ultrasound Therapeutics Laboratories

The Image-guided Ultrasound Therapeutic Laboratories (IgUTL) are located at the University of Cincinnati in the Heart, Lung, and Vascular Institute, a key component of efforts to align the UC College of Medicine and UC Health research, education, and clinical programs. These laboratories, directed by Christy K. Holland, comprise graduate and undergraduate students, postdoctoral fellows, physician-scientists, and clinical and scientific collaborators in fields including cardiology, neurosurgery, neurology, radiology, and emergency medicine. Holland’s research focuses on biomedical ultrasound including sonothrombolysis, ultrasound-mediated drug and bioactive gas delivery, development of echogenic liposomes, early detection of cardiovascular diseases, and ultrasound-image guided tissue ablation. Imaging algorithms incorporate both passive and active cavitation detection. The Biomedical Acoustics Laboratory within IgUTL, directed by T. Douglas Mast, investigates ultrasound imaging for therapy guidance, including echo decorrelation imaging for monitoring liver cancer ablation and real-time tracking of tongue motion for biofeedback in speech therapy. The Biomedical Ultrasonics and Cavitation Laboratory within IgUTL, directed by Kevin J. Haworth, employs ultrasound-mediated gas scavenging for image-guided treatment of cardiovascular disease, especially reperfusion injury. [Work supported by NIH Grants R01 NS047603, R01 HL135092, R01 HL133334, R01 CA158439, R01 DC017301, and K25 HL133452.]

Monitoring Microwave Ablation Using Ultrasound Echo Decorrelation Imaging: An ex vivo Study.

In this study, a microwave-induced ablation zone (thermal lesion) monitoring method based on ultrasound echo decorrelation imaging was proposed. A total of 15 cases of ex vivo porcine liver microwave ablation (MWA) experiments were carried out. Ultrasound radiofrequency (RF) signals at different times during MWA were acquired using a commercial clinical ultrasound scanner with a 7.5-MHz linear-array transducer. Instantaneous and cumulative echo decorrelation images of two adjacent frames of RF data were calculated. Polynomial approximation images were obtained on the basis of the thresholded cumulative echo decorrelation images. Experimental results showed that the instantaneous echo decorrelation images outperformed conventional B-mode images in monitoring microwave-induced thermal lesions. Using gross pathology measurements as the reference standard, the estimation of thermal lesions using the polynomial approximation images yielded an average accuracy of 88.60%. We concluded that instantaneous ultrasound echo decorrelation imaging is capable of monitoring the change of thermal lesions during MWA, and cumulative ultrasound echo decorrelation imaging and polynomial approximation imaging are feasible for quantitatively depicting thermal lesions.

Optimized Echo Decorrelation Imaging Feedback for Bulk Ultrasound Ablation Control.

Feasibility of controlling bulk ultrasound (US) thermal ablation using echo decorrelation imaging was investigated in ex vivo bovine liver. The first of two ablation and control procedures used a sequence of constant-intensity sonication cycles, ceased when the minimum echo decorrelation within a control region of interest (ROI) exceeded a predetermined threshold. The second procedure used a variable-intensity sonication sequence, with spatially averaged decorrelation as the stopping criterion. US exposures and echo decorrelation imaging were performed by a linear image-ablate array. Based on preliminary experiments, control ROIs and thresholds for the minimum-decorrelation and average-decorrelation criteria were specified. Controlled trials for the minimum-decorrelation and average-decorrelation criteria were compared with uncontrolled trials employing 9 or 18 cycles of matching sonication sequences. Lesion dimensions, treatment times, ablation rates, and areas under receiver operating characteristic curves were statistically compared. Successfully controlled trials using both criteria required significantly shorter treatment times than corresponding 18-cycle treatments, with better ablation prediction performance than uncontrolled 9-cycle and 18-cycle treatments. Either control approach resulted in greater ablation rate than corresponding 9-cycle or 18-cycle uncontrolled approaches. A post hoc analysis studied the effect of exchanging control criteria between the two series of controlled experiments. For either group, the average time needed to exceed the alternative decorrelation threshold approximately matched the average duration of successfully controlled experimental trials. These results indicate that either approach, using minimum-decorrelation or average-decorrelation criteria, is feasible for control of bulk US ablation. In addition, use of a variable-intensity sonication sequence for bulk US thermal ablation can result in larger ablated regions compared to constant-intensity sonication sequences.

Simulation and analysis of three-dimensional echo decorrelation imaging

A numerical model for pulse-echo ultrasound imaging [Mast, JASA 128:EL99-EL104, 2010] is extended to three-dimensional (3D) imaging of linear, weakly scattering continuum media by matrix array transducers. In this model, beam patterns for steered transmit and receive subapertures, calculated analytically under the Fresnel approximation, are combined with a 3D numerical tissue model to yield beamformed scan lines in a rectilinear or pyramidal configuration. Simulated scan lines are processed to yield both volumetric B-mode images and echo decorrelation images, comprising spatial maps of the normalized decorrelation between sequential pulse-echo image volumes. A method is demonstrated for construction and scan conversion of quantitative 3D echo decorrelation images such that, as for 2D echo decorrelation imaging [Hooi et al., JASA 137:585-597, 2015], the mapped echo decorrelation consistently estimates the local decoherence spectrum of the tissue reflectivity. Simulated 3D echo decorrelation images of random media are shown to accurately estimate known decoherence distributions that simulate heating effects in thermal ablation. Effects of factors including transducer frequency, scan configuration, and simulated lesion size on accuracy of decoherence estimates are tested. Applications to 3D monitoring of radiofrequency and microwave ablation are discussed.

In vivo ultrasound thermal ablation controlled using echo decorrelation imaging

The utility of echo decorrelation imaging feedback for real-time control of in vivo ultrasound thermal ablation was assessed in rabbit liver with VX2 tumor. High-intensity focused ultrasound (HIFU) and unfocused (bulk) ablation was performed using 5 MHz linear image-ablate arrays. Treatments comprised up to nine lower-power sonications, followed by up to nine higher-power sonications, ceasing when the average cumulative echo decorrelation within a control region of interest exceeded a predefined threshold (−2.3, log10-scaled echo decorrelation per millisecond, corresponding to 90% specificity for tumor ablation prediction in previous in vivo experiments [Fosnight et al., Ultrasound Med. Biol. 43:176-186, 2017]). This threshold was exceeded in all cases for both HIFU (N = 13) and bulk (N = 8) ablation. Controlled HIFU trials achieved significantly smaller average lesion width compared to previous uncontrolled trials. Both controlled HIFU and bulk ablation trials required significantly less treatment time than uncontrolled trials. Prediction of local liver and VX2 tumor ablation using echo decorrelation was tested using receiver operator characteristic curve analysis, showing prediction capability comparing favorably with uncontrolled trials. These results indicate that control using echo decorrelation imaging may reduce treatment duration and increase treatment reliability for in vivo thermal ablation.

Real-Time Spatiotemporal Control of High-Intensity Focused Ultrasound Thermal Ablation Using Echo Decorrelation Imaging in ex Vivo Bovine Liver

The ability to control high-intensity focused ultrasound (HIFU) thermal ablation using echo decorrelation imaging feedback was evaluated in ex vivo bovine liver. Sonications were automatically ceased when the minimum cumulative echo decorrelation within the region of interest exceeded an ablation control threshold, determined from preliminary experiments as −2.7 (log-scaled decorrelation per millisecond), corresponding to 90% specificity for local ablation prediction. Controlled HIFU thermal ablation experiments were compared with uncontrolled experiments employing two, five or nine sonication cycles. Means and standard errors of the lesion width, area and depth, as well as receiver operating characteristic curves testing ablation prediction performance, were computed for each group. Controlled trials exhibited significantly smaller average lesion area, width and treatment time than five-cycle or nine-cycle uncontrolled trials and also had significantly greater prediction capability than two-cycle uncontrolled trials. These results suggest echo decorrelation imaging is an effective approach to real-time HIFU ablation control.

Real-time feedback control of high-intensity focused ultrasound thermal ablation using echo decorrelation imaging

The feasibility of controlling high-intensity focused ultrasound (HIFU) thermal ablation in real time using echo decorrelation imaging feedback was investigated in ex vivo bovine liver. Sonication cycles (5.0 MHz, 0.7 s per HIFU pulse, 20-24% duty, 879-1426 W/cm2 spatial-peak, and temporal peak intensity) performed by a linear image-ablate array were repeated until the minimum cumulative echo decorrelation within the focal region of interest exceeded a predefined threshold. Based on preliminary experiments (N = 13), a threshold of −2.7 for the log10-scaled echo decorrelation per millisecond was defined, corresponding to 90% specificity of local ablation prediction. Controlled HIFU thermal ablation experiments (N = 10) were compared with uncontrolled experiments employing 2, 5, or 9 sonication cycles. Controlled trials showed significantly smaller average lesion area (4.78 mm2), lesion width (1.29 mm), and treatment time (5.8 s) than 5-cycle (7.02 mm2, 1.89 mm, 14.5 s) or 9-cycle (9.31 mm2, 2.4 mm, 26.1 s) uncontrolled trials. Prediction of local ablation using echo decorrelation was assessed using receiver operator characteristic (ROC) curve analysis, in which controlled trials showed significantly greater prediction capability (area under the ROC curve AUC = 0.956) compared to 2-cycle uncontrolled trials (AUC = 0.722). These results suggest that ablation control using echo decorrelation may improve the precision, reliability, and duration of ultrasound-guided HIFU treatments.

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

In open surgical procedures, image-ablate ultrasound arrays performed thermal ablation and imaging on rabbit liver lobes with implanted VX2 tumor. Treatments included unfocused (bulk ultrasound ablation, N = 10) and focused (high-intensity focused ultrasound ablation, N = 13) exposure conditions. Echo decorrelation and integrated backscatter images were formed from pulse-echo data recorded during rest periods after each therapy pulse. Echo decorrelation images were corrected for artifacts using decorrelation measured prior to ablation. Ablation prediction performance was assessed using receiver operating characteristic curves. Results revealed significantly increased echo decorrelation and integrated backscatter in both ablated liver and ablated tumor relative to unablated tissue, with larger differences observed in liver than in tumor. For receiver operating characteristic curves computed from all ablation exposures, both echo decorrelation and integrated backscatter predicted liver and tumor ablation with statistically significant success, and echo decorrelation was significantly better as a predictor of liver ablation. These results indicate echo decorrelation imaging is a successful predictor of local thermal ablation in both normal liver and tumor tissue, with potential for real-time therapy monitoring.

Dependence of ultrasound echo decorrelation on local tissue temperature during ex vivo radiofrequency ablation

This study investigates echo decorrelation imaging, an ultrasound method for thermal ablation monitoring. The effect of tissue temperature on the mapped echo decorrelation parameter was assessed in radiofrequency ablation experiments performed on ex vivo bovine liver tissue. Echo decorrelation maps were compared with corresponding tissue temperatures simulated using the finite element method. For both echo decorrelation imaging and integrated backscatter imaging, the mapped tissue parameters correlated significantly but weakly with local tissue temperature. Receiver operating characteristic (ROC) curves were used to assess the ability of echo decorrelation and integrated backscatter to predict tissue temperature greater than 40, 60, and 80 °C. Significantly higher area under the ROC curve (AUROC) values were obtained for prediction of tissue temperatures greater than 40, 60, and 80 ° C using echo decorrelation imaging (AUROC and 0.966) compared to integrated backscatter imaging (AUROC and 0.832).