Iodipimide ethyl ester (IDE) can be formulated as dense spherical particles with narrow diameter distribution. When IDE particles are injected intravenously, the Kupffer cells of the hepatic sinusoids accumulate particles within 10 to 20 minutes, after which the clearance and excretion of IDE takes place. During the uptake phase, the dense particles act as scattering sites, increasing the echogenicity of normal liver tissue. In comparison, tumors and other lesions remain at pre-injection echogenicity, as they lack Kupffer cells and therefore do not retain particles. This report provides initial studies of contrast enhancement in rabbit livers with implanted VX2 tumors, scanned in vivo and evaluated ex vivo using pulse-echo techniques. The distribution of particles within hepatic lobules may explain why the observed echogenicity is greater than that predicted by single-particle backscatter theory. Directions for future improvements are discussed.