Effect of PET image reconstruction techniques on unexpected aorta uptake

INTRODUCTION: To determine if unexpected aorta uptake seen in some patients is influenced by popular modern reconstruction algorithms using semi-quantitative and qualitative analysis.
METHODS: 25 consecutive patients without suspected vascular disease were selected for FDG PET-CT scanning and images of the aorta created using Iterative reconstruction (IT), IT + time of flight (TOF), IT+TOF+point spread function (PSF) correction (referred collectively as UHD) with and without metal artefact reduction (MAR) algorithms. An experienced radiologist created aorta and blood pool ROIs then copied these to all reconstructions for accurate positioning before recording target Aorta SUVmax and background Blood Pool (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 ± sd 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).
DISCUSSION AND 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 compared with UHD or UHD+MAR reconstructions. Harmonisation of techniques with a larger patient cohort is recommended in future clinical trials.