Fig. 2.

Molecular MRI of inflammation in healing myocardial infarcts. a–c Direct imaging of infiltrating macrophages. T2*-weighted images of mice 96 h after infarction and the intravenous injection of 3 mg iron per kg (a) or 20 mg iron per kg (b) of CLIO-Cy5.5. T2*-weighted imaging produces negative contrast enhancement in the injured myocardium (open arrows); reproduced with permission from [10]. c Off-resonance imaging of iron oxide accumulation within the macrophages infiltrating infarcted myocardium produces positive contrast (solid arrow); reproduced with permission from [24]. d, e Imaging of enzymes produced by the infiltrating macrophages. A myeloperoxidase activatable Gd chelate has been injected into mice with healing infarcts. d The chelate is activated by myeloperoxidase in the infarct producing positive contrast. e Only mild signal enhancement is seen in a heterozygous myeloperoxidase mouse, and f no enhancement is seen in the homozygous knockout mouse. Reproduced with permission from [26]