Sensitivity improvement of subharmonic-based pressure measurement using phospholipid-coated monodisperse microbubbles

Ultrason Sonochem. 2024 Feb 23;104:106830. doi: 10.1016/j.ultsonch.2024.106830. Online ahead of print.ABSTRACTThe use of the subharmonic signal from microbubbles exposed to ultrasound is a promising safe and cost-effective approach for the non-invasive measurement of blood pressure. Achieving a high sensitivity of the subharmonic amplitude to the ambient overpressure is crucial for clinical applications. However, currently used microbubbles have a wide size distribution and diverse shell properties. This causes uncertainty in the response of the subharmonic amplitude to changes in ambient pressure, which limits the sensitivity. The aim of this study was to use monodisperse microbubbles to improve the sensitivity of subharmonic-based pressure measurements. With the same shell materials and gas core, we used a flow-focusing microfluidic chip and a mechanical agitation method to fabricate monodisperse (∼2.45-µm mean radius and 4.7 % polydisperse index) and polydisperse microbubbles (∼1.51-µm mean radius and 48.4 % polydisperse index), respectively. We varied the ultrasound parameters (i.e., the frequency, peak negative pressure (PNP) and pulse length), and found that there was an optimal excitation frequency (2.8 MHz) for achieving maximal subharmonic emission for monodisperse microbubbles, but not for polydisperse microbubbles. Three distinct regimes (occurrence, growth, and saturation) were identified in the response of the subharmonic amplitude to increasing PNP for bot...

Source: Ultrasonics Sonochemistry - March 3, 2024 Category: Chemistry Authors: Pengcheng Wang Chunjie Tan Xiang Ji Jingfeng Bai Alfred C H Yu Peng Qin Source Type: research