» Perflutren Protein-Type A Microspheres Injectable Suspension is a sterile, nonpyrogenic suspension of microspheres produced by dispersing perflutren (octafluoropropane) gas in an aqueous solution of diluted sterile Albumin Human. It contains not less than 0.8 percent and not more than 1.2 percent protein. It may contain stabilizers, but contains no preservatives.