4149Coronary CT angiography with selective PET perfusion imaging guides referral for invasive coronary angiography and revascularization in coronary artery disease

Background:The positron emission tomography (PET) radiotracer 18F-sodium fluoride (18F-NaF) preferentially binds to areas of microcalcification.We have previously demonstrated vascular 18F-NaF uptake in human carotid and coronary atherosclerosis that correlates with necrotic inflammation and plaque rupture.In patients with abdominal aortic aneurysm (AAA), we assessed whether 18F-NaF PET-CT can predict AAA growth and clinical outcomes.Methods: We compared 18F-NaF uptake in normal and aneurysmal aortae between 20 patients with AAA and 20 control volunteers without AAA matched for age, sex and smoking status.In a prospective observational cohort study, 72 patients with AAA >40 mm anteroposterior diameter underwent 18F-NaF PET-CT, CT angiogram and calcium scoring.18F-NaF uptake was quantified using tissueto-background ratio (TBR).Patients with AAA were followed up with ultrasound for at least 1 year.The primary endpoints were aneurysm expansion and the composite of AAA repair or rupture.Results: Higher 18F-NaF uptake was observed within the AAA, both when compared to the controls (p=0.023)and within non-aneurysmal regions of the abdominal aorta in patients with AAA (p=0.004).18F-NaF uptake was similar in the thoracic aorta (p=0.970) and the non-aneurysmal aorta (p=0.911) of patients and controls.In the observational cohort, patients with AAA were predominantly elderly (73±7 years) men (85%) with a baseline aneurysm diameter of 48.8±7.7 mm.During 510±196 days of follow-up, there were 19 aneurysm repairs (26.4%) and 3 ruptures (4.2%).18F-NaF uptake in the most-diseased segment (MDS) of the aneurysm was associated with future growth rate (p=0.006)even after adjustment for age, sex, baseline diameter, blood pressure and body-mass index (p=0.042).Aneurysms in the highest tertile of 18F-NaF uptake expanded 2.5 times more rapidly than those in the lowest tertile (3.10 [3.58] vs 1.24 [2.41] mm/year, p=0.008) and were more than twice as likely to experience AAA repair or rupture (15.3% vs 5.6%, log-rank p=0.043).The association between 18F-NaF uptake (log2MDS TBRmax) and risk of repair or rupture remained even after adjustment for age, sex, gender, blood pressure, body-mass index and aneurysm diameter (HR 2.49, 95% CI1.07, 5.78; p=0.034).In contrast, the CT calcium scoring (Agatston score) was not associated with aneurysm expansion or events (both p>0.05).Conclusions: For the first time, we have demonstrated that 18F-NaF PET-CT is a novel approach to the identification of disease activity in patients with AAA and predicts the rate of aneurysm growth and clinical events, independent of established clinical risk factors including aneurysm diameter.