Microbubble-based scans reach beyond liver

Ultrasound is the most commonly used abdominal imaging modality. The addition of color and spectral Doppler imaging has been particularly beneficial. When ultrasound findings are nonspecific, however, patients are generally referred to CT or MRI. A contrast-enhanced ultrasound examination could alleviate the need for these more expensive imaging investigations, and a number of micro-bubble-based agents exist. The predominant agent used in Europe is SonoVue (Bracco). Other available agents include Definity (Bristol-Myers Squibb) and Optison (GE Healthcare). All microbubbles are filled with gas; sulfur hexachloride in the case of SonoVue, perfluoropro-pane in the case of Definity. The gas-filled bubbles are smaller than red blood cells, so they will undergo pulmonary recirculation. When injected intravenously, the micro-bubbles remain in the blood pool for up to six minutes.1 Technological advances, particularly the advent of harmonic and pulse-inversion imaging, have contributed to improvements in microbubble-based imaging. All major manufacturers of ultrasound equipment offer add-on software packages that allow for contrast-enhanced imaging, albeit at an extra cost. Microbubble contrast agents have an excellent safety profile and can be used in patients with renal impairment.2 Many clinical radiology departments across Europe now use micro-bubble contrast agents for ultrasound scans of the liver. Published guidelines are available on the characterization of focal liver lesions using contrast-enhanced ultrasound,3,4 and good concordance with CT and MRI has been demonstrated.5 The extension of contrast-enhanced ultrasound into other abdominal structures outside of the liver is on the horizon, though the potential role for microbubble agents in these organs is not as well appreciated at present. The agents may be used to depict disease processes in the spleen, kidneys, gallbladder, bowel, and pancreas.