Ultrasound single-phase CBE imaging for monitoring radiofrequency ablation of the liver tumor: A preliminary clinical validation

Abstract

Radiofrequency ablation (RFA) is an alternative treatment for early-stage hepatocellular carcinoma (HCC). The production of gas bubbles by RFA indicates threshold temperature of tissue necrosis and results in changes in backscattered energy (CBE) when ultrasound monitors RFA. In this study, ultrasound single-phase CBE imaging was used as a means of monitoring RFA of the liver tumor by analyzing the backscattering of ultrasound from gas bubbles in the liver. A total of 19 HCC patients were enrolled in the study. An ultrasound system was used during RFA to monitor the ablation process and acquire raw image data consisting of backscattered signals for single-phase CBE imaging. On the basis of single-phase CBE imaging, the area corresponding to the range of gas bubbles was compared with the tumor sizes and ablation zones estimated from computed tomography. During RFA, ultrasound single-phase CBE imaging enabled improved visualization of gas bubbles. Measured gas bubble areas by CBE were related to tumor size (the Spearman correlation coefficient rs = 0.86; p < 0.05); less dependent on the ablation zone. Approximately 95% of the data fell within the limits of agreement in Bland-Altman plots, and 58% of the data fell within the 95% CI. This study suggests that single-phase CBE imaging provides information about liver tumor size because of the abundant vessels in liver tumors that promote the generation of gas bubbles, which serve as natural contrast agents in RFAs to enhance ultrasound backscattering. Ultrasound single-phase CBE imaging may allow clinicians to determine if the required minimum RFA efficacy level is reached by assessing gas bubbles in the liver tumors.

Ultrasound Homodyned-K Contrast-Weighted Summation Parametric Imaging Based on H-scan for Detecting Microwave Ablation Zones

“…The QUS methods eliminate the necessity of upgrading the ultrasound device and enhance the feasibility of algorithms, which have the potential of real-time monitoring in the peri-ablation period. Different QUS approaches aim to identify the boundaries of the ablation coagulation zones, including ultrasonic backscattered energy, 16,17 ultrasonic attenuation coefficient, 18,19 ultrasound scatterer property parameters, 20,21 ultrasound echo decorrelation, [22][23][24][25] ultrasound radiofrequency echo time series analysis, 26,27 thermotherapy ultrasonic view, 28,29 ultrasound information entropy, 30 and ultrasonic envelope statistics. [31][32][33][34][35][36] Among them, the method of envelope statistics is to model the echo envelope signal by utilizing the probability distribution function (PDF), 37 and extract the parametric map which can visualize the ablated zone.…”