The Influence of Different Gases on Acoustic Properties of a Spherosome‐Based Ultrasound Contrast Agent (BY963)

Ultrasound contrast agents improve the signal‐to‐noise ratio of reflected ultrasound, enhancing the diagnostic value of transcranial Doppler (TCD). In dog studies, we investigated the time course of TCD signal amplitude after application of a phospholipid‐containing ultrasound contrast agent (BY963) filled with different gases. The median time of Doppler amplitude enhancement exceeding 5 dB was determined using isoflurane‐, isopentane‐, trichlortrifluoroethane‐, air‐, argon‐, and perfluoropentane‐filled BY963 (69, 72, 75, 78, 88, and 245 seconds respectively). The decrease of time‐intensity curve and the duration of signal enhancement showed significant differences comparing the different gases (p = 0.04 and 0.03, respectively). The time course of in vitro stability of BY963 agitated with the different gases measured by absorbance of light (500 nm) showed a retarded decay for perfluoropentane, a rapid decrease for air, isopentane, trichlortrifluoroethane, and argon, and a very rapid decrease using isoflurane. The time course of the different gases depended on the physicochemical properties (lipophilicity and the solubility in water) of the gas encoated in the phospholipid shell. Perfluoropentane‐filled BY963 showed the highest in vitro stability and the longest duration of TCD enhancement compared with the other gases used.