【Objective】 To prepare and optimize nanoscale bubble ultrasound contrast agent for stable ultrasonic imaging

and to evaluate its enhancing imaging capability in vitro and in vivo.【Methods】 Nanoscale bubbles were prepared by multiple-step methods: film-hydration

sonication and ventilation

low-speed centrifugal classifier. In order to screen out the optimal experimental conditions for small diameter and good repeatability

orthogonal test was designed aimed to main factors. The bubble morphology was observed under light microscopy

the nanobubble size was assessed by the Zeta 90Plus/BI-MAS Brookhaven. The contrast enhancement effect was observed in vitro and in vivo.【Results】Nanoscale bubbles with spherical shape distributed homogeneously

without obvious aggregation. The range of diameters was (238.6-340.7) nm

with the mean diameters of (276.0 ± 24.1) nm and average zeta potential of (-14.0 ± 0.6) mV. In vitro test in CPS mode nanoscale bubbles showed stable imaging. When turned to grayscale mode with high mechanical index

the bubbles were destroyed immediately with smaller diameters

and the enhancement of the image receded. Contrast imaging in vivo showed that the nanoscale ultrasound contrast agent could significantly enhance echo intensity of the vessels and parenchyma in rat livers and kidneys.【Conclusion】This kind of novel stable and small size nanoscale ultrasound contrast agent

which were easily destroyed in gray-scale mode with high mechanical index

would lay a foundation for extravascular tumor targeting imaging and local drug delivery.