B-mode enhancement of the liver with microbubble contrast agent: a blinded study in rabbits with VX2 tumors.

RATIONALE AND OBJECTIVES: The purpose of this study was to evaluate the accuracy of contrast material-enhanced sonography in the detection of liver lesions by using an animal model. MATERIALS AND METHODS: A total of 36 rabbits, 12 normal and 24 with one, two, or more VX2 tumors implanted percutaneously, were imaged on an Acuson 128XP/10 with a 7-MHz sector transducer by a sonographer blinded to the study assignments. The sonographer assigned rabbits to four groups (no, one, two, more than two tumors) based on the number of lesions detected before and then after the intravenous bolus injection of 0.5 mL of AF0150. S-VHS video segments or pre- and postcontrast images were separated, randomized, and evaluated by a blinded reader. Necropsy served as the gold standard. RESULTS: Classification of rabbits as normal or tumor bearing on the precontrast images produced three false-positive results and three false-negative results for the blinded sonographer and six false-positive results and two false-negative results for the blinded reader. On postcontrast images, all rabbits were correctly classified by both observers. The correlation of the classification of whether rabbits had no, one, two, or more tumors relative to the pathologic classification on precontrast images was poor to fair (K = 0.349 +/- 0.099 for the sonographer and 0.274 +/- 0.111 for the reader), whereas the postcontrast correlation was good to excellent (K = 0.924 +/- 0.099 for the sonographer and 0.809 +/- 0.076 for the reader). CONCLUSION: AF0150 markedly increased the ability of the sonographer and the blinded reader to distinguish normal from tumor-bearing animals and improved the classification of rabbits with more than one liver tumor.

Assessment of liver and kidney enhancement with a perfluorocarbon vapor-stabilized US contrast agent.

RATIONALE AND OBJECTIVES: The authors evaluated the time-echogenicity response of liver, kidney, and implanted VX2 tumor after injection of a microbubble contrast medium and assessed use of an avascular lesion as an internal standard. MATERIALS AND METHODS: Twenty-one New Zealand White rabbits were studied. To evaluate use of an internal standard and the dose-response relationship, nine rabbits with 7-day-old avascular liver lesions created by alcohol ablation received 0.1, 0.25, 0.5, and 1.0 mL of AF0145, a microbubble contrast agent. To evaluate tumor echogenicity, 12 rabbits implanted with VX2 tumor in the liver (six also underwent alcohol ablation) received 0.5 mL of AF0145. Videodensitometry was used to analyze echogenicity changes over 10 minutes. RESULTS: Echogenicity of the alcohol-ablated liver was not affected by contrast material administration. Liver and kidney echogenicity relative to ablation increased linearly with dose, peaking 1 minute after injection and decaying to baseline over 9 minutes. Contrast material administration defined the size and margins of VX2 lesions more clearly. In the arterial phase, the tumor rim was hyperechoic relative to surrounding liver, becoming isoechoic during the portal venous phase then hypoechoic during the late phase parenchymal phase. CONCLUSIONS: Lesions created by alcohol ablation can be used as an internal standard for quantitative analysis of adjacent tissues. AF0145 enhances perfused tissues, including vascular tumors, at gray-scale, real-time ultrasonography and enhances the liver.