Small-animal PET of 68Ga-NOTA-RGD in mice bearing SNU-C4 xenografts at 1 and 2 h after injection without or with cold c(RGDyK) (a and b, respectively). Arrows indicate tumor positions. Reprinted by permission of the Society of Nuclear Medicine from: Jeong JM, et al. (2008) Preparation of a promising angiogenesis PET imaging agent: 68Ga-labeled c(RGDyK)-isothiocyanatobenzyl-1,4,7-triazacyclononane-1,4,7-triacetic acid and feasibility studies in mice. J Nucl Med 49:830–836