Carotid atherosclerotic plaques standardised uptake values: software challenges and reproducibility

BACKGROUND Positron emission tomography-computed tomography (PET-CT) carotid standardised uptake values (SUV) of 18F-fluorodeoxyglucose (18FDG) have been proposed as an inflammatory biomarker for determining cerebrovascular diseases such as stroke. Consideration of varying methodological approaches and software packages is critical to the calculation of accurate SUVs in cross-sectional and longitudinal patient studies. The aim of this study was to investigate whether or not carotid atherosclerotic plaque SUVs are consistent and reproducible between software packages. 18FDG-PET SUVs of carotids were taken in 101 patients using two different software packages. Quality assurance checks were performed to standardise techniques before commencing the analysis where data from five to seven anatomical sites were measured. A total of ten regions of interest were drawn on each site analysed. Statistical analyses were then performed to compare SUV measurements from the two software packages and to explore reproducibility of measurements. Lastly, the time taken to complete each analysis was measured and compared. RESULTS Statistically significant differences in SUV measurements, between the two software packages, ranging from 9 to 21.8% were found depending on ROI location. In 79% (n = 23) of the ROI locations, the differences between the SUV measurements from each software package were found to be statistically significant. The time taken to perform the analyses and export data from the software packages also varied considerably. CONCLUSIONS This study highlights the importance of standardising all aspects of methodological approaches to ensure accuracy and reproducibility. Physicians must be aware that when a PET-CT data set is analysed, subsequent follow-ups must be verified, if possible, with the same software package or cross-calibration between packages should be performed.