Abstract 1905: Quantification Of Macrophages In Atherosclerotic Plaques Of Rabbits Using The Novel Specific Ct Contrast Agent N1177: A Comparison With 18f-fdg Uptake On Pet-ct And Histology

Abstract

Introduction. N1177 is a novel computed tomography (CT) contrast agent taken up by macrophages. Purpose. We tested if the enhancement detected on CT in aortic wall of rabbits 2 hours after injection of N1177 correlates with metabolic activity measured with 18F-FDG uptake on positron emission tomography (PET)-CT and macrophage area on histology. Methods. Atherosclerotic plaques were induced in the aorta of 7 New-Zealand White rabbits by a repeated balloon injury (4 weeks apart) and 4 months of hyperlipemic diet. Three non-injured rabbits fed a chow diet were used as controls. A CT of the aorta (n=10) was acquired in each rabbit before and 2 hours after intravenous injection of N1177 (250 mg iodine/kg). One week later, the same rabbits were imaged on a PET-CT 3 hours after injection of 1 mCi/kg of 18F-FDG. Enhancement of the aortic wall after injection of N1177 was compared to the SUV on PET-CT, and to macrophage area on immunohistochemistry (anti-RAM-11 antibody) of corresponding sections. Results. A significant higher enhancement was measured on N1177-enhanced CT in the aortic wall of atherosclerotic compared to control rabbits (mean increase of 10.0 ± 5.2 Hounsfield Units vs. 2.0 ± 2.1 HU, respectively; p<0.05). We found a strong correlation between the enhancement of the aortic wall measured on N1177-enhanced CT (Fig .: before (A) and 2 hours after (B) injection of N1177) and FDG uptake on PET-CT (Fig. C ; r=0.61, p<0.001), macrophage area on immunohistology (Fig. D ; r=0.63, p<0.001). Conclusion. Enhancement detected in the aortic wall of rabbits with N1177-enhanced CT correlated with intense metabolic activity measured with 18-F-FDG on PET-CT and with macrophage area on histology.