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BR1: A New Ultrasonographic Contrast Agent Based on Sulfur Hexafluoride-Filled Microbubbles
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1995
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Sulfur hexafluoride microbubbles provide greater resistance to pressure changes during systole compared to air-filled bubbles. BR1 is a lyophilized sulfur hexafluoride microbubble agent that, when reconstituted, yields a suspension of 2 × 10⁸ microbubbles/mL with a mean diameter of 2.5 µm, whose physicochemical and acoustic properties were characterized and whose diagnostic performance was tested in minipigs. More than 90 % of BR1 microbubbles are <8 µm, the agent remains highly echogenic and stable for over 8 h, maintains consistent echogenicity across 1–10 MHz, and produces homogeneous, dose‑dependent left‑heart opacification in animals, indicating a promising ultrasound contrast agent.
The basic characteristics of BR1, a novel echo contrast agent based on stabilized sulfur hexafluoride (SF6) microbubbles have been evaluated.The authors determined the physicochemical properties (bubble concentration, bubble size distribution, resistance to pressure, and stability) and the acoustic properties (backscatter and attenuation coefficients) of BR1. The diagnostic value of BR1 was evaluated further in minipigs. Left heart images were recorded before and after injection of different doses of BR1.BR1 is formulated as a lyophilized product, which after addition of saline, provides a suspension containing 2 x 10(8) SF6 microbubbles/mL with a number mean diameter of 2.5 microns. More than 90% of the bubbles are below 8 microns. The use of SF6 rather than air provides an improved resistance to pressure increases such as the ones occuring in the left heart during systole. After reconstitution, the echogenicity and the bubble characteristics are unchanged for more than 8 hours. The high echogenicity remains almost constant over the entire medical frequency range (1-10 MHz). BR1 injections in animals resulted in a homogenous, dose-dependent opacification of the left heart.Considering its high echogenicity, outstanding stability, and resistance to pressure changes, BR1 is a very promising ultrasound contrast agent.