CXC motif chemokine receptor 4 (CXCR4) and its ligand stromal cell-derived factor-1a have been shown to be involved in the orchestration of postinfarct inflammation and its resolution in patients with acute myocardial infarction (AMI)(1). Recently, pilot visualization of CXCR4-expression using a radiolabeled PET ligand ([68Ga] Pentixafor) could be demonstrated in patients after AMI (2, 3). The aim of this study was to further investigate CXCR4 expression after myocardial ischemia in comparison to cardiac magnetic resonance (CMR). From January 2015 to June 2016, 22 patients (17 men and 5 women, mean age 61 Æ 11 years) with (sub) acute myocardial infarction underwent imaging with [68Ga] Pentixafor-positron emission tomography (PET)/computed tomography (CT) and CMR (21 patients, 1 patient excluded because of adipositas permagna) within 2 to 13 days after onset of symptoms (median delay between PET and CMR: 1 day). Thirteen patients returned for follow-up CMR (1 to 14 months; median: 4 months). A total of 75 Æ 15 min after injection of 116 Æ 29 MBq of [68Ga] Pentixafor, PET/CT was performed (2). Images were first inspected visually. For semi-quantitative analysis, the axial PET image slice with maximum cardiac uptake was selected. A standardized 10-mm circular region was placed over the area with the peak activity to derive maximum and peak standardized uptake values. For signal-tobackground ratios, peak standardized uptake values were also derived in normal reference regions by a second region of interest (diameter: 10 mm) in a remote region of the left ventricular wall without late-gadolinium-enhancement (LGE) in the corresponding CMR data. For multi-organ analysis of [68Ga] Pentixafor uptake, mean standardized uptake values were also derived for bone marrow (thoracic vertebrae) and spleen. These PET parameters were then correlated with clinical(creatine kinase[CK], troponin T, leukocyte, and C-reactive protein levels) as well as with CMR parameters.

CMR was performed on a 1.5-T (n ¼ 7)(Achieva 1.5-T, Philips Healthcare, Best, the Netherlands) and 3.0-T (n ¼ 15)(Achieva DS 3.0-T, Philips Healthcare) scanner using dedicated protocols (2). In analogy to PET, LGE and T2-weighted images were analyzed for