18 F-FDG-PET/CT assessment of Takayasu arteritis and effect of time-of-flight reconstruction: an observational study

Abstract Background To assess the impact of time-of-flight (TOF) positron emission tomography (PET)/computed tomography (CT) image reconstruction on assessment of Takayasu arteritis (TKA). We reviewed 14 patients (15 cases) who underwent TOF-PET/CT. PET images were reconstructed using ordered-subsets expectation maximisation ± TOF. Uptake in 10 vascular regions was assessed using the four-point visual grading system (3, higher than liver uptake; 0, no uptake). The grades in the TOF-PET/CT and non-TOF-PET/CT groups were compared using the sign test. Relationships between visual grade and arterial FDG uptake pattern in the 10 regions and clinical findings were assessed. Results Except for the highest visual grade, the visual grades in all regions were significantly higher in the TOF-PET/CT group (p=0.003). FDG uptake pattern and region were not significant determinants of the effect of TOF reconstruction. Assessment of disease activity was inconsistent between the groups in 6 (4%) of 150 regions when grade 2/3 was defined as active and in 5 (3.3%) of 150 when grade 3 was defined as active. Conclusions Visual grades were significantly higher in all regions when assessed by TOF-PET/CT. Use of the same reconstruction algorithm before and after treatment is recommended when evaluating the response to treatment.