Imaging of integrin alphavbeta3 expression.

The integrin alphavbeta3 plays an important role in angiogenesis and tumor metastasis. It is expressed on activated endothelial cells as well as some tumor cells. Therefore it is a promising imaging target as a potential surrogate parameter of angiogenic activity. Molecular imaging of alphavbeta3 expression could potentially facilitate response evaluation of antiangiogenic drugs (e. g. bevacizumab) or aid in selecting and monitoring patients receiving humanized monoclonal antibody therapies directed against alphavbeta3 (EMD121974). Therefore many different approaches for imaging of alphavbeta3 expression have been studied in the recent years, including positron emission tomography (PET), single photon emission tomography (SPECT), magnetic resonance imaging (MRI), optical imaging and ultrasound using targeted microbubbles. While optical imaging techniques lend themselves for preclinical studies, PET and SPECT using the alphavbeta3 specific tracers [(18)F]galacto-RGD and [(99m)Tc]NC100692 are the only techniques up to now which have been successfully used in patients. The various advantages and disadvantages of several imaging techniques will be discussed in this article.