Detection of Macrophages in Aortic Aneurysms by Nanoparticle Positron Emission Tomography–Computed Tomography

Abstract

Objective— Current management of aortic aneurysms (AAs) relies primarily on size criteria to determine whether invasive repair is indicated to preempt rupture. We hypothesized that emerging molecular imaging tools could be used to more sensitively gauge local inflammation. Because macrophages are key effector cells that destabilize the extracellular matrix in the arterial wall, it seemed likely that they would represent suitable imaging targets. We here aimed to develop and validate macrophage-targeted nanoparticles labeled with fluorine-18 (¹⁸F) for positron emission tomography–computed tomography (PET-CT) detection of inflammation in AAs. Methods and Results— Aneurysms were induced in apolipoprotein E^−/− mice via systemic administration of angiotensin II. Mice were imaged using PET-CT and a monocyte/macrophage–targeted nanoparticle. AAs were detected by contrast-enhanced micro-CT and had a mean diameter of 1.85±0.08 mm, whereas normal aortas measured 1.07±0.03 (PP18F-labeled nanoparticles allows quantitation of macrophage content in a mouse model of AA.