Narrow size distribution of microbubbles for enhancement of harmonic imaging

An ultrasound microbubble contrast agent is a promising technique in clinical diagnosis because ultrasound in combination with microbubbles enhances the ultrasound backscatter to produce an increased contrast images. In this study, we developed phospholipid-based microbubbles showing a relatively narrow size distribution of 0.8-1.3 μm. The optimal resonance frequency of developed microbubbles was determined to be 2.5-3.0 MHz by measuring echo signals at various frequencies. Ultrasound harmonic imaging was performed in a vessel phantom at the optimal resonance frequencies. Microbubble contrast-enhanced ultrasound images visualized a vessel tube clearly and demonstrated much improved image quality, compared to the control. In conclusion, the ultrasonography in the harmonic mode is capable of maximally resonating micrbubbles with a narrow size distribution at a specific frequency for enhanced ultrasound imaging.