Different behaviors of microbubbles in the liver: time-related quantitative analysis of two ultrasound contrast agents, Levovist and Definity

The differences in time-related changes of liver images were compared quantitatively between Levovist and Definity. A total of 40 rabbits were assigned to eight groups according to the timing of taking enhanced liver images at 1, 3, 5, 7, 9, 11, 13 and 15 min by intermittent harmonic imaging using Levovist or Definity (30 microL/kg) and another 40 rabbits for Definity (50 microL/kg). Intensity changes between before and after enhancement in the portal vein (I-PV) and liver parenchyma (I-LP) were analyzed. I-PV was greater than I-LP at the 1- and 3-min phases of enhancement and I-LP became greater than I-PV with Levovist after 5 min. However, I-PV was higher than I-LP in all phases with Definity. Different time-intensity curves of these two agents will indicate discrete behaviors of microbubble hemodynamics in the liver; Levovist becomes accumulated in the liver, whereas Definity acts as a blood pool contrast agent, without accumulation.