Aortic Uptake of 18F-NaF and 18F-FDG and Calcification Predict the Development of Abdominal Aortic Aneurysms and Is Attenuated by Drug Therapy.

Background: Abdominal aortic aneurysms expand over time and increase the risk of fatal ruptures. To predict expansion, the isolated assessment of ¹⁸F-fluorodeoxyglucose (FDG) and sodium fluoride (NaF) uptake or calcification volume in aneurysms has been investigated with variability in results. We systematically evaluated whether ¹⁸F-FDG and ¹⁸F-NaF uptake was predictive of abdominal aortic aneurysm expansion.

Methods: Seventy-four male Sprague-Dawley rat abdominal aortic aneurysm models were imaged using positron emission tomography-computed tomography with ¹⁸F-FDG and ¹⁸F-NaF at 1, 2, 4, 6, and 8 weeks after CaCl₂ or saline stimulation. In the 1-week cohort (n=25), the correlation between ¹⁸F-FDG or ¹⁸F-NaF uptake and pathological markers was investigated. In the time course cohort (n=49), animals received either atorvastatin, losartan, aldactone, or risedronate to assess the effect of these drugs, and the relationship between aortic size and sequential ¹⁸F-FDG and ¹⁸F-NaF uptake or calcification volume was examined.

Results: In the 1-week cohort, the maximum standard unit value of ¹⁸F-FDG and ¹⁸F-NaF uptake correlated with CD68- (r=0.82; P=0.001) and von Kossa staining-positive areas (r=0.89; P<0.001), respectively. In the time course cohort, ¹⁸F-FDG and ¹⁸F-NaF uptake changed in a time-dependent manner and drugs attenuated this uptake. Specifically, ¹⁸F-FDG showed high uptake at weeks 1 and 2, whereas a high ¹⁸F-NaF uptake was noted throughout the study period. Atorvastatin and risedronate showed a decreased and increased aortic size, respectively. The final aortic area correlated well with ¹⁸F-FDG and ¹⁸F-NaF uptake and calcification volume, especially at 1 and 2 weeks (¹⁸F-NaF [1 week]: r=0.61, ¹⁸F-FDG [2 weeks]: r=0.51, calcification volume [1 week]: r=0.59; P<0.001). Multiple linear regression analysis showed that the combination of these factors predicted the final aortic size, with ¹⁸F-NaF uptake at 1 week being the strongest predictor.

Conclusions: The uptake of ¹⁸F-NaF and ¹⁸F-FDG and the calcification volume at appropriate times correlated with the development of abdominal aortic aneurysms, with ¹⁸F-NaF uptake being the strongest predictor.