Assessment of different quantification metrics of [ 18 F]-NaF PET/CT images of patients with abdominal aortic aneurysm

Background We aim to assess the spill-in effect and the benefit in quantitative accuracy for [ 18 F]-NaF PET/CT imaging of abdominal aortic aneurysms (AAA) using the background correction (BC) technique. Methods Seventy-two datasets of patients diagnosed with AAA were reconstructed with ordered subset expectation maximization algorithm incorporating point spread function (PSF). Spill-in effect was investigated for the entire aneurysm (AAA), and part of the aneurysm excluding the region close to the bone (AAA exc ). Quantifications of PSF and PSF+BC images using different thresholds (% of max. SUV in target regions-of-interest) to derive target-to-background (TBR) values (TBR max , TBR 90 , TBR 70 and TBR 50 ) were compared at 3 and 10 iterations. Results TBR differences were observed between AAA and AAA exc due to spill-in effect from the bone into the aneurysm. TBR max showed the highest sensitivity to the spill-in effect while TBR 50 showed the least. The spill-in effect was reduced at 10 iterations compared to 3 iterations, but at the expense of reduced contrast-to-noise ratio (CNR). TBR 50 yielded the best trade-off between increased CNR and reduced spill-in effect. PSF+BC method reduced TBR sensitivity to spill-in effect, especially at 3 iterations, compared to PSF ( P -value ≤ 0.05). Conclusion TBR 50 is robust metric for reduced spill-in and increased CNR.