CXCR4 and myocardial infarction: Based on the observation that our tracer signal peaked at the time point of maximum inflammation in the infarcted animals, points to a high probability that most of the CXCR4 signal is derived from leukocytes.26 This is in agreement with previous data, where the 68Ga-Pentixafor signal in the infarct area 3 days post MI was associated with increased detection of macrophages and granulocytes by immunostaining.