Effect of PET Image Reconstruction Techniques on Unexpected Aorta Uptake

Objectives:

To determine if unexpected aorta uptake seen in some patients is influenced by popular modern reconstruction algorithms using semi-quantitative and qualitative analysis.
Methods:

Twenty-five consecutive patients without suspected vascular disease were selected for 18F-FDG positron emission tomography/ computed tomography (PET/CT) scanning and images of the aorta were created using iterative reconstruction (IT), IT + time of flight (TOF), IT + TOF + point spread function correction (referred collectively as UHD) with and without metal artefact reduction (MAR) algorithms. An experienced radiologist created aorta and blood pool (BP) regions of interests then copied these to all reconstructions for accurate positioning before recording target aorta standardized-uptake-values (SUVₘₐₓ) and background BP SUVₘₑₐₙ. Furthermore, target-to-background ratio (TBRₘₐₓ) was defined by aorta SUVₘₐₓ-to-BP SUVₘₑₐₙ ratio for more analysis.
Results:

For aorta SUVₘₐₓ with IT, IT + TOF, UHD, UHD + MAR reconstructions the mean ± standard deviation recorded were 2.15±0.43, 2.25±0.51, 2.25±0.45 and 2.09±0.4, respectively. Values for BP SUVₘₑₐₙ were 1.61±0.31, 1.58±0.28, 1.58±0.28 and 1.47±0.25, respectively. Likewise, for TBRₘₐₓ these were 1.35±0.19, 1.43±0.21, 1.43±0.19, 1.43±0.18, respectively. ANOVA analysis revealed no significant differences for aorta SUVₘₐₓ (F(0.86) p=0.46), BP SUVₘₑₐₙ (F(1.22) p=0.31) or TBRₘₐₓ (F(0.99) p=0.4). However, the qualitative visual analysis revealed significant differences between IT + TOF with UHD (p=0.02) or UHD + MAR (p=0.02).
Conclusion:

Reconstruction algorithm effect on aorta SUVₘₐₓ or BP SUVₘₑₐₙ or TBRₘₐₓ was not statistically significant. However, qualitative visual analysis showed significant differences between IT + TOF as compared with UHD or UHD + MAR reconstructions. Harmonization of techniques with a larger patient cohort is recommended in future clinical trials.