Acoustic modulation of contrast agents for hepatic flow differentiation

Current methods of liver metastasis diagnosis involve an intravenous (IV) bolus injection of CT contrast agent, with detection in the liver parenchyma using a time differential in enhancement. Recent studies have shown that ultrasound measurements of time to initial enhancement and time to and level of peak enhancements with an IV bolus of contrast agent can be diagnostic. Research presented here demonstrates a technique in which arterial modulation of contrast can be realized with leading and trailing edge characteristics similar to an IA injection, using an externally applied acoustic field and continuous IV infusion. In vivo experiments with New Zealand White rabbits were performed using a perfluorocarbon-based ultrasound contrast agent infused into an ear vein at 10 μL/kg/min. An acoustic field applied to the abdominal aorta was used to control the flow of the contrast agent. Spectral Doppler images of the abdominal aorta and hepatic vein and grayscale harmonic images of the aorta and liver parenchyma were collected.