[{"from": "human", "value": "Please give me some details about this molecule. [C][Branch1][=Branch2][C][Branch1][C][F][Branch1][C][F][F][Branch1][=Branch2][C][Branch1][C][F][Branch1][C][F][F][Branch1][C][F][F]"}, {"from": "gpt", "value": "The molecule is a fluorinated hydrocarbon and gaseous substance used as an imaging contrast agent. After administration in microsphere form, perflutren exhibits lower acoustic impedance than blood and improves ultrasound signaling."}]