KDR and neoplasm: Preclinical and clinical studies demonstrated the feasibility of functional and molecular CEUS imaging with VEGFR2 (vascular endothelial growth factor receptor 2) targeted MB in monitoring therapy response to anti-angiogenic treatment in different tumor entities [11,17–21], as VEGF is one of the most potent growth factors of endothelial cells and a main regulator of angiogenesis [22–24].