Advances in Diagnostic Ultrasound: Contrast-Enhanced Ultrasound Imaging

Conventional (non-contrast-enhanced) ultrasound imaging is widely accepted as a valuable imaging modality for a broad range of applications. Ultrasound is low in cost relative to modalities such as angiography, CT, and MRI, and it uses non-ionizing radiation, making it safe for examination of even the most sensitive tissues such as the developing fetal brain. The modality's high safety profile and broad applicability make it widely available. However, ultrasound has several limitations, including low tissue-contrast resolution, susceptibility to artifacts that can obscure anatomy, and a lack of specificity for some abnormalities, which affect its diagnostic potential and how it is utilized for patient care.

The addition of contrast media to the ultrasound exam has the potential to overcome some of the limitations of conventional ultrasound and offers additional benefits.

Contrast-enhanced ultrasound (CEUS) imaging uses specialized contrast agents along with contrast-specific ultrasound imaging modes to improve assessment of blood flow and tissue vascularity. The ultrasound contrast agents (UCAs) are injected intravenously into the patient while the structure or region of interest is scanned. Microbubbles in the UCA increase the reflectivity of the blood, enhancing the ultrasound image.

UCAs have been approved by FDA for more than 20 years, but their indication has been limited to cardiac applications: to opacify the left ventricular chamber of the heart in patients with suboptimal echocardiograms to enhance images of the ventricular endocardial border (Appis et al. 2015). Details can be found in Overview of Injectable Suspensions for Contrast-enhanced Echocardiography from ECRI Institute's Health Technology Assessment Information Service (HTAIS; membership required for access).

In April 2016, Lumason (Bracco Diagnostics Inc., Princeton, NJ) became the first intravenously administered UCA to gain FDA approval for a noncardiac (also referred to as radiologic) indication: for characterization of focal liver lesions in adults and pediatric patients. And in January 2017, Lumason was also approved for ultrasonography of the urinary tract in pediatric patients for evaluating suspected or known vesicoureteral reflux. For that indication, Lumason is administered directly into the urinary bladder, not intravenously.

Although the FDA-approved indications for UCAs are limited, physicians can elect to use UCAs for off-label applications; numerous reports describe the clinical value of UCAs when used for off-label indications (Barr 2013, Fleischer et al. 2009, Rafailidis et al. 2017, Rosado et al. 2016, Sparchez et al. 2015). And use in other countries is less restricted. The use of CEUS for both cardiac...