Nakagami Statistics-Based Parametric Thermoacoustic Imaging for Assessment of Liver Microwave Ablation.

Thermal ablation is an effective treatment for primary liver cancer, but intraoperative assessment of ablation efficacy remains a clinical challenge. Microwave-induced thermoacoustic imaging (TAI) offers high tissue contrast based on dielectric properties, whereas conventional delay-and-sum reconstruction often yields limited contrast between ablated and normal tissue. To improve the contrast, we present a post-processing parametric imaging method that applies Nakagami statistics to thermoacoustic signal envelopes. The Nakagami shape parameter m is sensitive to thermal-ablation-induced alterations in tissue microstructural features. This work represents a new attempt to extract parametric images from thermoacoustic signal envelopes for intraoperative ablation assessment. In vitro and in vivo experiments were conducted to evaluate this Nakagami-based approach. Compared with conventional TAI, Nakagami images exhibited markedly improved contrast between the ablation zone and normal tissue. Quantitative analysis using pathological images as the gold standard demonstrated higher accuracy for Nakagami-based TAI across all measurements: 91.08% vs. 85.22% (in vitro diameter), 86.76% vs. 74.50% (in vitro area), 85.44% vs. 76.52% (in vivo diameter), and 79.22% vs. 72.72% (in vivo area). These findings suggest that Nakagami statistics-based TAI improves ablation zone characterization by capturing tissue microstructural information, showing potential as a tool for intraoperative assessment of liver ablation efficacy.