18F–Sodium Fluoride Uptake in Abdominal Aortic Aneurysms
Does fluorine-18–sodium fluoride (18F-NaF) positron emission tomography and computed tomography (PET-CT) predict abdominal aortic aneurysm (AAA) growth and clinical outcomes?
In prospective case-control (n = 20/group) and longitudinal cohort (n = 72) studies, patients with AAA (aortic diameter >40 mm) and control subjects (diameter <30 mm) underwent abdominal ultrasound, 18F-NaF PET-CT, CT angiography, and calcium scoring. Clinical endpoints were aneurysm expansion and the composite of AAA repair or rupture.
18F-NaF uptake was increased in AAA compared to nonaneurysmal regions within the same aorta (p = 0.004), or aortae of control subjects (p = 0.023). Histological and micro-PET-CT analysis demonstrated that 18F-NaF uptake localized to areas of aneurysm disease and active calcification. Aneurysms in the highest tertile of 18F-NaF uptake expanded 2.5 times more rapidly than those in the lowest tertile (3.10 [2.34-5.92] vs. 1.24 [0.52-2.92] mm/year, p = 0.008) and were nearly three times as likely to experience AAA repair or rupture (15.3% vs. 5.6%, log-rank p = 0.043).
18F-NaF PET-CT is a novel and promising approach to the identification of disease activity in patients with AAA, and may be clinically useful for predicting aneurysm growth and clinical outcomes.
The unpredictable natural history of AAA mandates imaging surveillance for all patients, some of whom do not exhibit aneurysm growth. The ability to predict which AAAs are most likely to grow (and, conversely, when growth is less likely), therefore, would benefit patients through more selective utilization of surveillance imaging and repair. This study suggests that 18F-NaF PET-CT holds potential to identify patients at increased risk for aneurysm growth and related clinical events, potentially adding an evaluation of biologic activity to the standard as diameter and morphology assessments provided by ultrasound or routine cross-sectional imaging.
It is interesting to note that the significance of the 18F-NaF PET-CT as a predictor of clinical events was diminished in models that included estimated glomerular filtration rate and peripheral artery disease (PAD) as covariates. Given that chronic kidney disease and PAD are both associated with inflammatory states, it may be that these observations were confounders rather than effect modifiers. Further investigation, therefore, will be needed to establish the additive benefit of 18F-NaF PET-CT alongside clinical risk factors.
Clinical Topics: Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Prevention, Vascular Medicine, Atherosclerotic Disease (CAD/PAD), Interventions and Imaging, Interventions and Vascular Medicine, Angiography, Computed Tomography, Nuclear Imaging
Keywords: Angiography, Aorta, Abdominal, Aortic Aneurysm, Abdominal, Diagnostic Imaging, Fluorine, Peripheral Arterial Disease, Positron-Emission Tomography, Renal Insufficiency, Chronic, Risk Factors, Secondary Prevention, Sodium Fluoride, Tomography, X-Ray Computed, Vascular Diseases
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