Developments of Ultrasound Multiscale Compounding Nakagami Imaging for Monitoring Radiofrequency Ablation and Detecting the Temperature Profile in the Tissue

Background: Radiofrequency ablation (RFA) is the most used alternative modality for the minimally invasive liver tumor treatment. Ultrasound image is commonly used for guiding the insertion of the electrode since it provides real-time and effective monitoring of electrode location. High power RFA (HPRFA) induces air bubbles in the ablation zone because heating is fast and the temperature is high, corresponding to hyperechoic patterns in the ultrasound image. Low power RFA (LPRFA) increases the tissue temperature but does not produce significant formation of bubbles in the ablation zone. Therefore, various ultrasound imaging modes can be responsible for evaluating the ablation regions caused by the HPRFA (B-mode) and LPRFA (temperature imaging), respectively. Challenges: HPRFA would produce a strong shadow effect in the lower portion of the ablation region, making ultrasound B-scan fail to monitor the RFA. Ultrasound temperature imaging is used to monitor the temperature distribution for evaluating LPRFA. However, constructing a reliable temperature image requires additional speckle tracking and compensation of the echo shifts, making the evaluation of temperature profile complex and difficult. To date, there is no any imaging method that can be used to support monitoring both HPRFA and LPRFA. Strategies: Recently, we found that ultrasound Nakagami parametric imaging has the ability to detect the backscattered information in the shadow region and has great potentials to allow ultrasound temperature estimation and temperature profile visualization without echo shift compensation. This finding encourages us to organize this 3-year research proposal to develop a novel multifunctional Nakagami imaging method with high resolution and the capabilities of detecting the backscattered information in the shadow region and visualizing the temperature distribution. Goals: In the first year, we will develop multiscale compounding (MSC) Nakagami imaging as the core technique in this proposal, and the performances in the detection of scatterer concentration, resolution, edge detectability, and smoothness will be examined by simulations and phantom experiments. In the second year: we will study the temperature effect on the MSC Nakagami image and the feasibility of temperature imaging method based on the MSC Nakagami image. In the third year: we will carry out ablation experiments based on tissue samples and animals to investigate the performance of using the MSC Nakagami image to monitor the HPRFA and LPRFA.

Project ID:PB10207-0372
External Project ID:NSC102-2221-E182-008