Bolus versus continuous infusion of microbubble contrast agent for liver US: initial experience

Institutional review board approval and informed consent were obtained. To prospectively assess if continuous infusion of galactose-palmitic acid can prolong the duration of hepatic enhancement at ultrasonography over bolus injection, 11 patients received two injections--one bolus injection (2 mL/sec) and one continuous infusion (1.5 mL/min)--with the same dose of galactose-palmitic acid (4 g, 300 mg/dL). Two unenhanced baseline sweep scans (mechanical index of 0.7 and 1.3) of the relevant liver lobe were acquired followed by contrast-enhanced sweeps after bolus injection and continuous infusion. Each sweep was saved as cine loops and analyzed with a personal computer. Duration of enhancement more than 3 dB was prolonged by continuous infusion from 4.3 minutes +/- 2.4 (+/-standard deviation) at bolus injection to 10.1 minutes +/- 3.0 (P < .005). Maximal parenchymal enhancement was 11.0 dB +/- 3.2 (bolus injection) and 9.2 dB +/- 3.8 (infusion, P < .05). Peak liver-to-lesion contrast was 14.2 dB +/- 6.3 (bolus injection) and 13.2 dB +/- 7.1 (infusion, not significant). Continuous infusion of galactose-palmitic acid markedly prolongs but slightly diminishes hepatic enhancement; liver-to-lesion contrast remains unchanged.