Objective:To investigate the value of using ultrasound excited contrast agents to assess extracorporeal hydrostatic pressure on the basis of ultrasound contrast imaging.Methods:An extracorporeal hydrostatic pressure evaluation system was established. The changes in contrast intensity was first evaluated for the same concentration of microbubble contrast agent at ambient pressures of 20, 25, 30, 35, 40, and 45 cmH 2O. Contrast agents with the same initial intensity were placed at different pressures for 1 s, 3 s, and 5 s, and the percentage change in contrast agent intensity was analyzed to select the optimal excitation time. Finally, the contrast agent at different pressures was stimulated using an acoustic excitation device, and correlation analysis was performed using the Pearson product moment correlation coefficient. Linear regression analysis was used to establish the relationship between different pressures and the percentage change in intensity. Results:When the ambient pressure was varied under 6 gradients of 20, 25, 30, 35, 40, and 45 cmH 2O, the contrast strength decreased with the pressure increased, and there was a negative correlation between contrast strength and the pressure ( r=-0.971, P<0.001). Under different pressures, the contrast agent intensity showed different degrees of natural decrease in 1 s, 3 s, and 5 s. The difference in the percentage change in contrast agent intensity in each pressure gradient was not statistically significant in 1 s ( P>0.05), whereas the differences in the percentage change in contrast agent intensity in 3 s and 5 s were statistically significant in each pressure gradient (all P<0.05). After microbubble contrast agent was stimulated by ultrasound excitation for 1s, the percentage change in contrast agent intensity was significantly correlated with ambient pressure ( r=-0.976, P<0.001). A linear regression model was fitted with the percentage change in contrast agent intensity after 1 s of stimulation as the independent variable and the pressure as the dependent variable, with the model equation: y=60.075-2.559×x1, where x1 is the percentage change in contrast agent ( R2=0.952, P<0.001). Conclusions:The percentage change in contrast intensity after 1 s of ultrasound excitation of microbubble contrast agent is a favorable predictor of hydrostatic pressure at 6 pressure gradients of 20, 25, 30, 35, 40, and 45 cmH 2O, which may provide a new method for noninvasive monitoring of portal vein pressure for clinicans.