161 18F-Sodium Fluoride Positron Emission Tomography in Acute Aortic Syndrome

Background Acute aortic syndrome is a catastrophic condition characterised by medial degeneration and cellular destruction within the aortic wall. 18F-Sodium fluoride (18F-NaF) positron emission tomography (PET) detects microscopic calcification as a marker of disease activity. This proof-of-concept study aims characterise 18F-NaF PET in patients with acute aortic syndrome. Methods Aortic tissue obtained from patients with acute aortic syndrome was stained using von Kossa’s stain for calcium-phosphate complexes and then exposed to 18F-sodium fluoride to confirm radiotracer binding to microcalcification. Next, patients with aortic dissection or intramural haematomas and healthy controls underwent 18F-NaF PET/CT and CT angiography of the aorta. A threshold of 12 weeks since diagnosis was used to classify patients to ‘recent’ or ‘prior’ acute aortic syndrome groups. Peak aortic 18F-NaF uptake was corrected for background blood pool activity to obtain a most-diseased segment tissue-to-background ratio (MDS TBRmax). Radiotracer binding was compared with aortic size in a linear regression model and major adverse aortic events (aortic rupture, aorta-related death or aortic repair) in a proportional hazards Cox survival analysis. Results Aortic 18F-NaF uptake co-localized with histologically defined regions of microcalcification (n=15). Patients with acute aortic syndrome had increased 18F-NaF binding compared to healthy controls (TBRmax 2.02±0.42 (n=47) vs 1.36±0.39 (n=20) respectively, p<0.001). Peak radiotracer uptake occurred at the site of intimal disruption (+27.5% compared to the proximal aorta, p<0.001). 18F-NaF binding to the false lumen was associated with aortic growth (+7.1 mm/yr, p=0.011) and uptake in the outer aortic wall was associated with major adverse aortic events (hazard ratio 8.6 [95% CI, 1.1-68.1], p=0.041) in patients with recent acute aortic syndrome. Conclusion 18F-NaF PET/CT uptake was increased in patients with acute aortic syndrome at sites of disease activity. Radiotracer binding was associated with aortic growth and clinical events. 18F-NaF PET-CT holds promise as a non-invasive marker of disease severity and future risk in patients with acute aortic syndrome. Conflict of Interest None