5,855,865, describes methods for making protein microspheres encapsulating certain perfluorocarbon gases, such as perfluoropropane
, by ultrasonic or mechanical cavitation in the absence of oxygen.
6-9) Sulfurhexafluoride (SF6) and perfluoropropane
(C3F8) are the most commonly used gases.
The PTO's order granting MBI's petition specifically noted that the prior art teaches the use of Freon(R) gases in ultrasound imaging, and that perfluoropropane
is a Freon(R) gas.
The patent also covers methods of forming microbubbles containing perfluoropropane
, perfluorobutane, perfluoropentane, perfluoroheptane and other fluorochemicals.
5,562,893, is titled "Gas-filled Microspheres with Fluorine Containing Shells," and covers ultrasound imaging agents which comprise hydrocarbon and perfluorocarbon gases, such as perfluoropropane
, perfluorobutane, perfluoropentane within fluorine containing shells.
While these PFCs -- halocarbons 116, 14, and 23; sulfur hexafluoride; nitrogen trifluoride; and perfluoropropane
-- are essential to many manufacturing processes, many environmental scientists believe they may last as long as 50,000 years when released into the atmosphere.