Objective   To prepare the poly lactic-co-glycolic acid (PLGA) microbubble ultrasonic contrast agent and evaluate its physicochemical and acoustic properties.  Methods   Different PLA/LGA microbubble ultrasonic contrast agents were prepared with the double emulsion method. Their physicochemical properties and acoustic signal intensity change were evaluated in vitro using different doses and mechanical index (MI) of PLGA microbubble ultrasonic contrast agent.  Results   A cream white suspension was obtained by dissol

ving the white PLGA microbubble powders in saline or PBS with a pH value of 6.5±0.3. Light microscopy showed that the microbubbles were uniform in size and well dispersed. The average diameter of microbubbles was 1.2 μm. Coulter count showed that the concentration of 0.01 g polymicrobubble dry powders dissolved in 10 ml distilled water was 2.0×10

9

/ml -4.0×10

9

/ml. No significant difference was observed in concentration

diameter and pH value in 10 weeks after the PLGA microbubbles were kept at 4℃ or at common temperature. In vitro study showed that the acoustic intensity of PLGA microbubbles increased with their concentration

and was linearly correlated with their mechanical index (MI). Rabbit cardioroentgenography showed that PLGA microbubbles passed through the pulmonary circulation and achieved the left ventricular imaging in vivo. A significant difference was found in left ventricle acoustic intensity when the MI value was 0.2 compared with when it was 0.6

1.0

and 1.2.  Conclusion   PLGA microbubble ultrasonic contrast agent has a rather good controllability and stability with a higher resonance frequency

thus being able to pass through the pulmonary circulation and achieve left ventricular imaging. 