Science to practice: the dawn of molecular US imaging for clinical cancer imaging

Ultrasonography (US) is one of the most commonly used diagnostic modalities in clinical medicine. Gas-filled microbubbles can be used to enhance the contrast of tumors by indicating increased vascularity. Because microbubbles can be detected with high sensitivity and specificity, they fulfill an important precondition for use as a molecular imaging probe. Over the past several years, there have been an increasing number of published studies that showed that markers of angiogenesis and inflammation can be assessed reliably when microbubbles are coupled to antibodies and peptides. Recently, target-specific microbubbles have been developed that are suited for use in humans. Now the identification of the optimal clinical indications for molecular US imaging in clinics is required. In this context, advantages and limitations of US with targeted microbubbles, when compared with other imaging modalities, must be carefully considered. Because US is a transportable, cheap, real-time imaging modality, molecular US imaging may have advantages for initial tumor screening and US-guided interventions; furthermore, it may support therapy monitoring in intervals between whole-body images obtained with positron emission tomography (PET), computed tomography (CT), and magnetic resonance (MR) imaging.