Portal Vein Pressure Estimation and Portal Hypertension Discrimination Based on Subharmonic Scattering of Ultrasound Contrast Agent Microbubbles

—Objective: The acquisition of real-time portal vein pressure (PVP) is important for portal hypertension (PH) discrimination to monitor disease progress and select treatment options. To date, the PVP evaluation approaches are either invasive or noninvasive but with less stability and sensitivity. Methods: We customized an open ultrasound scanner to explore in vitro and in vivo the ultrasound contrast agent SonoVue microbubbles’ subharmonic characteristics with acoustic pressure and local ambient pressure, and obtained promising results of PVP measurements in canine models with induced PH by ligation or embolization of portal vein. Results: In in vitro experiments, the highest correlations between the subharmonic amplitude of SonoVue microbubbles and ambient pressure were observed at acoustic pressures of 523 kPa and 563 kPa (r = −0.993, −0.993, P<0.05, respectively). The correlation coefficients between absolute subharmonic amplitudes and PVP (10.7–35.4 mmHg) were the highest among existing studies using microbubbles as pressure sensors (r values ranged from −0.819 to −0.918). The PH (>16 mmHg) diagnostic capacity also achieved a high level (563 kPa, sensitivity = 93.3%, specificity = 91.7%, accuracy = 92.6%). Conclusion: This study proposes a promising measurement for PVP with the highest accuracy, sensitivity, and specificity in an in vivo model compared to existing studies. Future investigations are planned to assess the feasibility of this technique in clinical practice. Significance: This is the first study that comprehensively investigates the role of the subharmonic scattering signals from SonoVue microbubbles in evaluating PVP in vivo. It represents a promising alternative to invasive measurements for portal pressure.