Hepatic vasculature flow monitoring through the ultrasonic interruption of contrast agents

Abstract

A technique has been developed to assess differential liver perfusion due to hepatic artery versus portal vein. This technique uses a continuous intravenous infusion of contrast agent and transcutaneous ultrasound to control the flow of contrast agent in selected vessels. A 1-in diameter transducer controlled the flow of perfluorocarbon-filled contrast agent in the abdominal aorta. It has been previously shown that acoustic amplitudes required to manipulate contrast agent are well within FDA limits. Pulsed ultrasound 10-cycle tonebursts at 2.25 MHz and 2.7% duty cycle were applied to the abdominal aorta for 30 sec to clear contrast agent from the hepatic artery, portal vein and liver parenchyma. The interruption transducer was then turned off, creating a sharp leading edge of contrast agent, with risetimes of approximately 0.1 sec measured in the hepatic artery. Harmonic grayscale and spectral Doppler images were obtained on a Toshiba Powervision 8000. The sharp contrast agent leading edge allows differential measurements of hepatic artery and portal vein arrival times. This time differential was measured at approximately 10 sec. These results indicate that image-guided insonification of the abdominal aorta may substantially improve discrimination of the hepatic arterial and portal venous supply in hepatic imaging.