Azami Roozbeh H, Yapar Mehmet, Halder Saikat, Forsberg Flemming, Eisenbrey John R, Sarkar Kausik
Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC, USA.
Department of Radiology, Thomas Jefferson University, Philadelphia, PA, USA.
Ultrasound Med Biol. 2025 Feb;51(2):373-380. doi: 10.1016/j.ultrasmedbio.2024.11.006. Epub 2024 Nov 24.
Subharmonic Aided Pressure Estimation (SHAPE) is a noninvasive technique for estimating organ-level blood pressure using the strong correlation between the subharmonic signal and ambient pressure. The compressible gas core of microbubbles enables them to generate linear and nonlinear acoustic responses when exposed to ultrasound. Here, the sulfur hexafluoride (SF) gas core of SonoVue (known as Lumason in the United States), a clinical contrast agent, was exchanged with a perfluorobutane (PFB) core to investigate its effect on the SHAPE response.
Excitations of 25-700 kPa peak negative pressure (PNP) and 3 MHz transmission frequency were used to study in vitro the effects of overpressure changes ranging from 5 to 25 kPa (37-186 mm Hg).
Unlike SonoVue with SF, at low PNPs (<400 kPa), SonoVue with a PFB gas core exhibited no subharmonic at the atmospheric pressure, but during pressurization, a stable subharmonic response (maximum of 25 dB at 100 kPa PNP and 20 kPa Overpressure) appeared. SonoVue with a PFB gas core showed an increase in subharmonics with overpressure at high PNPs (>400 kPa), which was not observed before in normal SonoVue or other lipid microbubbles. With negligible size distribution difference between these two microbubbles, these effects on subharmonic generation are likely due to the gas core, casting new light on the mechanism by which ambient overpressure affects subharmonic.
This study may inform future SHAPE technique developments.
次谐波辅助压力估计（SHAPE）是一种利用次谐波信号与环境压力之间的强相关性来估计器官水平血压的非侵入性技术。微泡的可压缩气体核心使其在暴露于超声时能够产生线性和非线性声学响应。在此，将临床造影剂声诺维（在美国称为Lumason）的六氟化硫（SF）气体核心替换为全氟丁烷（PFB）核心，以研究其对SHAPE响应的影响。
使用峰值负压（PNP）为25 - 700 kPa且传输频率为3 MHz的激励，在体外研究5至25 kPa（37 - 186 mmHg）超压变化的影响。
与含SF的声诺维不同，在低PNP（<400 kPa）时，含PFB气体核心的声诺维在大气压下不显示次谐波，但在加压过程中，出现了稳定的次谐波响应（在100 kPa PNP和20 kPa超压下最大值为25 dB）。含PFB气体核心的声诺维在高PNP（>400 kPa）时随着超压次谐波增加，这在正常声诺维或其他脂质微泡中未曾观察到。由于这两种微泡的大小分布差异可忽略不计，这些对次谐波产生的影响可能归因于气体核心，为环境超压影响次谐波的机制提供了新的线索。
本研究可能为未来SHAPE技术的发展提供参考。
