Assessment of different quantification metrics of [F-18]-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 [F-18]-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 (TBRmax, TBR90, TBR(70)and TBR50) 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.