Can The Inflammatory Response Be Evaluated Using 18F-FDG Within Zones of Microvascular Obstruction Following Myocardial Infarction?
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
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Inflammation that occurs following acute myocardial infarction plays a pivotal role in "healing" by facilitating the creation of a supportive scar. (18)F-FDG, which is taken up avidly by macrophages, has been proposed as a marker of cell-based inflammation. However, its reliability as an accurate indicator of inflammation has not been established, particularly in the early post infarction period when regional myocardial perfusion is often severely compromised.
METHODS: Nine adult dogs underwent left anterior descending coronary occlusion with or without reperfusion. Animals were imaged between 7 to 21 days post infarction with Positron Emission Tomography/Magnetic Resonance Imaging (PET/MRI) following: a) bolus injection of Gd-DTPA, b) bolus injection of (18)F-FDG, c) bolus injection of 99Tc-DTPA to simulate the distribution of Gd-DTPA (which represents its partition coefficient in well perfused tissue) and d) the injection of (111)Indium-labeled white blood cells 24 hours earlier. Following sacrifice, myocardial tissue concentrations of (18)F, (111)In and 99Tc were determined in a well counter. Linear regression analysis evaluated the relationships between a) the concentrations of (111)In vs (18)F and b) the dependence of the ratio of (111)In/(18)F to the apparent distribution volume of (99m)Tc-DTPA.
RESULTS: In seven of the nine animals (111)In increased as (18)F increased with the other two animals showing weak negative slopes. With respect to the dependence of (111)In/(18)F with partition coefficient four animals showed no dependence and four showed a week positive slope with one animal showing a negative slope. Further, in regions of extensive microvascular obstruction, (18)F significantly underestimated the extent of the presence of (111)In.
CONCLUSION: In the early post myocardial infarction period, PET (18)F-FDG imaging following a single bolus administration may underestimate the extent and degree of inflammation within regions of microvascular obstruction.