Molecular imaging of angiogenesis after myocardial infarction by 111 In-DTPA-cNGR and 99m Tc-sestamibi dual-isotope myocardial SPECT

Background CD13 is selectively upregulated in angiogenic active endothelium and can serve as a target for molecular imaging tracers to non-invasively visualise angiogenesis in vivo. Non-invasive determination of CD13 expression can potentially be used to monitor treatment response to pro-angiogenic drugs in ischemic heart disease. CD13 binds peptides and proteins through binding to tripeptide asparagine-glycine-arginine (NGR) amino acid residues. Previous studies using in vivo fluorescence microscopy and magnetic resonance imaging indicated that cNGR tripeptide-based tracers specifically bind to CD13 in angiogenic vasculature at the border zone of the infarcted myocardium. In this study, the CD13-binding characteristics of an 111In-labelled cyclic NGR peptide (cNGR) were determined. To increase sensitivity, we visualised 111In-DTPA-cNGR in combination with 99mTc-sestamibi using dual-isotope SPECT to localise CD13 expression in perfusion-deficient regions.