In vivo mapping of vascular inflammation using the translocator protein tracer 18F-FEDAA1106

Abstract

Non-invasive imaging methods are required to monitor the inflammatory content of atherosclerotic plaques. FEDAA1106 (N-(5-fluoro-2-phenoxyphenyl)-N-(2-(2-fluoroethoxy)-5- methoxybenzyl) acetamide) is a selective ligand for TSPO-18kDa (also known as peripheral benzodiazepine receptor), which is expressed by activated macrophages. We compared 18F- FEDAA1106 and 18F-FDG (a marker of glucose metabolism) for PET imaging of vascular inflammation. This was tested using a murine model where focal inflammation was induced in the carotid artery via placement of a constrictive cuff. Immunostaining revealed CD68-positive cells (macrophages) at a disturbed flow site located downstream from the cuff. Dynamic PET imaging using 18F-FEDAA1106 or 18F-FDG was registered to anatomical data generated by CT/CT angiography. Standardized uptake values (SUV) were significantly increased at cuffed compared to contralateral arteries using either 18F-FEDAA1106 (p<0.01) or FDG (p<0.05). However, the 18F-FEDAA1106 signal was significantly higher at the inflamed disturbed flow

region compared to the non-inflamed uniform flow regions, whereas differences in FDG uptake were less distinct. We conclude that 18F-FEDAA1106 can be used in vivo for detection of vascular inflammation. Moreover, the signal pattern of 18F-FEDAA1106 correlated with vascular inflammation more specifically than FDG uptake.