Preliminary Findings from 18F-Sodium Fluoride Positron Emission Tomography/Computed Tomography in Acute Aortic Syndrome

Abstract

Introduction: Acute aortic syndrome (AAS) encompasses intramural haematoma, aortic dissection and penetrating aortic ulcer. Risk prediction following these conditions remains a challenge. 18F-Sodium Fluoride positron emission tomography / computed tomography (18F-NaF PET/CT) is a novel technique that detects microscopic vascular calcification beyond the resolution of CT alone. In abdominal aortic aneurysms, 18F-NaF PET/CT predicts aneurysm growth and risk of rupture or repair.1 This study aims to examine the utility of 18F-NaF PET/CT in acute aortic syndrome. Methods: Patients with a new diagnosis of AAS and those under surveillance for established acute aortic syndrome were prospectively recruited. The new diagnosis group had 18F-NaF PET/CT within 6 weeks of presentation. Peak radiotracer binding was measured from the aortic root to the aortic bifurcation. Uptake was corrected for background blood-pool activity to obtain a tissue-to-background ratio (TBR). 18F-NaF PET/CT was explored in relation to disease- and patient-related characteristics. ANOVA and linear regression were used for categorical and continuous variables respectively (*=p< 0.001). Results: A total of 3072 TBR measurements were made from 22 patients of median (range) age 65(38-75) years. Thirteen patients had aortic dissection, six had intramural haematoma and three a penetrating aortic ulcer. Substantially increased 18F-NaF binding was seen in all three pathologies (Figure 1): (TBR[95% CI]: 1.82[1.79-1.85] v 1.71[1.68-1.75]* v 2.13[2.02-2.25]*). 18F-NaF uptake was similar in the eight patients with a new diagnoses and 14 with established diagnoses, (TBR 1.83[1.79-1.86] v 1.85[1.82-1.90]; p=0.89). Sixteen patients with Stanford type-B disease had increased radiotracer uptake compared to six with type-A disease (TBR 1.88[1.84-1.91] v 1.75[1.71-1.80]*). Increased 18F-NaF was seen with advancing age*. No difference in radiotracer binding was seen between the 18 men and 4 women (TBR 1.84[1.81-1.87] v 1.84[1.79-1.88], p=0.697) (Figure 2). 18F-NaF uptake was independent of aortic diameter (>32mm v < 32mm: TBR 1.77[1.74-1.80] v 1.86[1.81-1.93];p=0.08), and was associated with increased calcium burden (Agatston score >1600 v < 1600: TBR 2.06[2.01-2.11] v 1.81[1.78-1.85]*). Individuals with endovascular repair (TEVAR: n=2) had aortic remodelling on CT. This group had reduced 18F-NaF uptake (TEVAR v no TEVAR: TBR 1.58[1.56-1.60] v 1.88[1.85-1.91]*). Conclusion: These novel data characterise the relationship between 18F-Sodium Fluoride PET/CT and acute aortic syndrome for the first time. 18F-NaF uptake was increased in all three sub-pathologies. Highest radiotracer binding was seen in penetrating aortic ulcers. 18F-NaF binding was independent of aortic diameter. 18F-NaF PET/CT may also detect aortic remodelling following endovascular repair.Fig 218F-Sodium Fluoride uptake in relation to disease- and patient-related characteristics.View Large Image Figure ViewerDownload Hi-res image Download (PPT) Disclosure: Nothing to disclose