Feasibility study of microwave‐induced thermoacoustic/ultrasound dual‐modality imaging for the assessment of nonalcoholic fatty liver disease

Abstract Background Accurate and non‐invasive diagnosis of nonalcoholic fatty liver disease (NAFLD) remains a critical challenge. Current methods are often costly, invasive, or lack sensitivity in early stages. Purpose To investigate the feasibility and accuracy of microwave‐induced thermoacoustic/ultrasound (TAI/US) dual‐modality imaging for the assessment of hepatic steatosis. Methods A microwave‐induced TAI/US dual‐modality imaging system with a microwave source at a center frequency of 3 GHz as an excitation source was applied to image rabbit NAFLD models, and the spleen‐to‐liver thermoacoustic amplitude ratio (TAR S‐L ) parameter was introduced to assess hepatic steatosis. Pathology was used as the gold standard, and Oil Red O staining fat fraction (ORO‐FF) was calculated by a semi‐quantitative software. Group differences in TAR S‐L across hepatic steatosis grades were assessed using the Kruskal–Wallis test with Dunn‐Bonferroni post hoc comparisons. The Mann–Whitney U test and Cliff's Delta (δ) were applied to compare dichotomized steatosis subgroups. Spearman's rank correlation coefficient was used to evaluate the association between TAR S‐L and ORO‐FF. Receiver Operating Characteristic (ROC) curve was performed to assess the diagnostic performance of TAR S‐L , and the results were quantified by the Area Under the Curve (AUC). A p < 0.05 was considered significant. Results The results demonstrated that the thermoacoustic and ultrasound images from the microwave‐induced TAI/US dual‐modality imaging system could be well‐fused. The median TAR S‐L values for normal (S0), mild (S1), moderate (S2), and severe (S3) steatosis were 1.110 (0.953–1.283), 1.260 (1.073–1.430), 1.740 (1.625–1.870), and 2.195 (1.833–2.580). TAR S‐L values increased with steatosis severity, showing a strong positive correlation with ORO‐FF ( r = 0.908, p < 0.001). Statistically significant differences with large effect sizes were observed in TAR S‐L between S0 vs. S3 and S1 vs. S3 ( p < 0.05, |Cliff's δ | > 0.474), indicating marked group differences. While comparisons such as S0 vs. S2 and S1 vs. S2 lacked statistical significance ( p > 0.05), large effect sizes (|Cliff's δ | > 0.474) suggest potential true differences limited by sample size. ROC analysis confirmed diagnostic performance, with AUC of 0.894 (0.764–1.000), 0.979 (0.931–1.000), and 0.953 (0.874–1.000) for distinguishing S0 vs. ≥S1, ≤S1 vs. ≥S2, and ≤S2 vs. S3, respectively. Conclusion At present, the diagnosis of NAFLD based on TAI still belongs to the research gap. Our study initially verified the potential of microwave‐induced TAI/US dual‐modality imaging combined with the thermoacoustic parameter TAR S‐L for the diagnosis of NAFLD. These findings establish a crucial methodological foundation for subsequent in‐depth investigations into the application of microwave‐induced TAI/US dual‐modality imaging in the quantitative diagnosis of hepatic steatosis.