In vivo quantification of cholesterol content in human carotid arteries by quantitative Gamma-camera imaging after injection of autologous low density lipoproteins (LDL)

Low density lipoprotiens (LDL) were isolated by immunoaffinity chromatography from 18 patients (31–70 years) suffering from primary hypercholesterolemia with angiographically proven atherosclerosis of either one or both carotid arteries. LDL were labeled with ¹²³I (1 mCi/mg LDL) by the iodine monochloride method followed by purification with dialysis and immediately reinjected thereafer. Gamma-camera serial controls over carotid regions allowed visual detection of uptake of the radiocompound uptake in 12 out of the 18 patients. The lipid entry ratio (LER; counts over the vascular region/pixel as compared to the contralateral side after background subtraction) confirmed the visual findings. Whole body images performed until 20 h after reinjection showed 3 different kinetic types of LDL-influx into the vessel wall: decreasing (type I), increasing and then decreasing (type II) and continuously increasing (type III) with time. Four patients underwent endarterectomy within 2–7 weeks after gamma-camera imaging. Histological control revealed an extensive amount of “foam cells” in tissue samples derived during surgery and an absence of endothelial lining in samples belonging to patients with type II kinetics.