Tissue-specific US contrast agent for evaluation of hepatic and splenic parenchyma

PURPOSE: To evaluate the recently developed ultrasonographic (US) contrast agent SHU 563A, which is specifically taken up by the reticuloendothelial s ystem (RES). MATERIALS AND METHODS: Color Doppler imaging (CDI) was performed in a gel p hantom, with SHU 563A microbubbles in stationary suspension. CDI was perfor med in vivo in five woodchucks with natural hepatomas and in 12 rabbits bef ore and after intravenous bolus injections of SHU 563A (0.16-0.48 mL/kg). A fter a 15-135-minute delay, the liver and spleen were scanned again, and th e image findings were compared with pathologic analysis results. RESULTS: Phantom CDI demonstrated a random mosaic color pattern in spite of the lack of flow. This phenomenon, which is associated with bubble rupture , is termed induced acoustic emission. In vivo, delayed imaging demonstrate d acoustic emission signals in normal parenchyma, whereas no mosaic color w as seen in regions lacking reticuloendothelial cells (eg, tumors). Four of 12 VX-2 tumors detected with pathologic analysis were detected with US alon e; the remaining eight tumors were detected by using US with contrast agent (100%, P = .0078). Nine of 20 hepatomas were detected at baseline US, wher eas 17 were detected after administration of SHU 563A (P = .0215). Acoustic emission enabled detection of hepatic tumors as smalt as 3 mm in diameter. CONCLUSION: CDI with SHU 563A demonstrates a random mosaic color pattern, e ven without flow The characteristic appearance of acoustic emission signals provides a distinctive method of visualizing normal hepatic tissues and su bstantially improves the detectability of hepatic tumors.