Ultrasonic Nakagami Imaging of High-intensity Focused Ultrasound-induced Thermal Lesions in Porcine Livers: Ex Vivo Study

Abstract

High-intensity focused ultrasound (HIFU) has demonstrated the capacity to be used for local thermal ablation in clinical surgery; however, relying solely on conventional ultrasound B-mode imaging to monitor HIFU thermal ablation and determine ablation levels remains a challenge. Here, we experimentally demonstrate the ability to use Nakagami imaging to monitor HIFU-induced thermal lesions in porcine livers ex vivo. Ultrasonic Nakagami imaging has been proven to be able to characterize tissues with different scatterer concentrations and distributions. The pathological sections from HIFU thermally ablated porcine liver tissues reveal that normal and denatured tissues significantly differ in scatterer concentration and distribution. Therefore, we believe that Nakagami imaging can be used to monitor thermal ablation by tracing Nakagami parameter changes in liver tissues. The ex vivo porcine liver experiments were performed using a homemade HIFU device synchronized with a commercial diagnostic ultrasound scanner to obtain the ultrasound envelope data before and after thermal ablation. These data were used to evaluate the performance of thermal lesion characterization using Nakagami imaging and were compared with those derived from conventional B-mode imaging. Experimental results showed that Nakagami imaging can be used to identify thermal lesions, which are difficult to visualize using conventional B-mode imaging because there is no apparent bubble formation. In cases with apparent bubble formation, Nakagami imaging could provide a more accurate estimation of lesion size and position. In addition, the Nakagami imaging algorithm is characterized by low computational complexity, which means it can be easily integrated as postprocessing for existing array imaging systems.

A Review of Quantitative Ultrasound-Based Approaches to Thermometry and Ablation Zone Identification Over the Past Decade

“…In the aspect of ablation zone identification, Zhang et al 66 first explored the feasibility of using Nakagami m -parametric imaging to evaluate thermal lesions in HIFU ablation of tissue-mimicking phantoms and found a significant effect on overcoming the shadow effect of bubbles 67 in the peri-ablation period. Rangraz et al 68 and Huang et al 69 used Nakagami m -parametric imaging to effectively detect the thermal lesions caused by HIFU ablation of porcine muscle and liver in vitro. Han et al 70 demonstrated that Nakagami m -parametric imaging could evaluate and differentiate thermal coagulation and cavitation erosion.…”

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

“…47 During thermal ablation, the statistical distribution of scatterers changed from simple to complex. 12,33 Modeling the backscattered envelope of scatterers with the HK distribution might be of more physical meaning. To the best of our knowledge, there was no work reported on HK parametric imaging using the FDC, so we investigated its feasibility and applied it to the MWA monitoring.…”

Ultrasound Backscatter Envelope Statistics Parametric Imaging for Liver Fibrosis Characterization: A Review

“…10 Quantitative ultrasound (QUS) has become an important technique for tissue characterization with quantified information, including spectral information, backscatter envelope statistics, scatterer properties, backscatter coefficient, and acoustic attenuation. [11][12][13][14][15][16][17][18][19][20][21][22][23] Backscatter coefficient has been investigated for liver fibrosis characterization. 24,25 Ultrasound backscatter envelope statistics parametric imaging is an important group of QUS techniques that have been applied to characterizing different kinds of tissue.…”

“…24,25 Ultrasound backscatter envelope statistics parametric imaging is an important group of QUS techniques that have been applied to characterizing different kinds of tissue. [11][12][13]15,[17][18][19][20][21][22] In particular, its application in liver fibrosis assessment has developed over the past two decades. However, a state-of-the-art review of ultrasound backscatter envelope statistics parametric imaging for liver fibrosis characterization has not been conducted.…”