B-mode enhancement of the liver with microbubble contrast agent: A blindedstudy in rabbits with VX2 tumors

Rationale and Objectives. The purpose of this study was to evaluate the acc uracy of contrast material-enhanced sonography in the detection of liver le sions by using an animal model, Materials and Methods. A total of 36 rabbits, 12 normal and 24 with one, tw o, or more VX2 tumors implanted percutaneously, were imaged on an Acuson 12 8XP/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 e valuated by a blinded reader. Necropsy served as the gold standard. Results. Classification of rabbits as normal or tumor bearing on the precon trast 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 th e classification of whether rabbits had no, one, two, or more tumors relati ve to the pathologic classification precontrast images was poor to fair (ka ppa = 0.349 +/- 0.099 for the sonographer and 0.274 +/- 0.111for the reader ), whereas the postcontrast correlation was good to excellent (kappa = 0.92 4 +/- 0.099 for the sonographer and 0.809 +/- 0.076 for the reader). Conclusion. AF0150 markedly increased the ability of the sonographer and th e blinded reader to distinguish normal from tumor-bearing animals and impro ved the classification of rabbits with more than one liver tumor.