Detection of atherosclerosis using a novel positron-sensitive probe and 18-fluorodeoxyglucose (FDG)

Inflammation contributes to atherosclerotic plaque remodeling, enlargement and rupture. Non-invasive imaging of coronary artery inflammation could hel p target therapy to 'vulnerable' atheromata, but is limited because of smal l tissue mass and arterial motion. Local radiopharmaceutical imaging may ov ercome some of these limitations. We used a positron-sensitive fiberoptic p robe, which can distinguish positron emissions from annihilation photons, t o identify diseased from healthy endothelium in an atherosclerotic model. N ew Zealand White rabbits underwent Fogarty-catheter injury of an iliac arte ry and then were fed a high-fat diet for 3 weeks. Fasted animals received 9 0-180 MBq of 18-fluorodeoxyglucose (FDG) 2-4 h before sacrifice and harvest of injured and uninjured iliacs. Arteries were incised longitudinally and the probe was placed in contact with the arterial intima. Multiple measurem ents were obtained along 1 cm artery segments in 60 s intervals, and correc ted for F-18 decay and background. Measurements were recorded over 93 injur ed and normal artery segments in 11 animals. Mean probe Z-scores were 4.8-f old higher (CI 3.4-6.3) over injury atherosclerosis compared with uninjured normal iliac artery segments (P < 0.001). Gamma counting confirmed that in jured artery segments accumulated more FDG per gram than did normal segment s (0.203%.kg injected dose per gram of tissue versus 0.042, P < 0.001). Non -arterial tissue also accumulated FDG avidly, particularly reticuloendothel ial tissues and blood. Delayed sacrifice, 4 h compared with 2 h after anima l FDG injection, further reduced blood background counts and improved the s ignal-to-noise ratio. Histopathology confirmed that injured iliac artery ha d significantly higher intimal and medial cross-sectional area compared wit h uninjured artery. Injured artery also had significantly higher macrophage and smooth muscle cell density. Positron-sensitive probe counts correlated with the intima to media ratio (r = 0.63, P = 0.03). Our positron-sensitiv e probe distinguishes atherosclerotic from healthy artery in a blood-free f ield. Intravascular study of plaque biology may be feasible using FDG and a positron-sensitive probe. ((C) 2001 Lippincott Williams & Wilkins).