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Time Course of Tumor SUV in 18F-FDG PET of Breast Cancer: Presentation of a Simple Model Using a Single Reference Point for Time Corrections of Tumor SUVs

Tumor standardized uptake values (SUVs) vary with the interval between 18F-FDG injection and image acquisition. This paper presents a simple method using a single reference point to make appropriate time corrections for tumor SUVs. Methods: The reference point method was algebraically deduced from observations made by Beaulieu et al., who found that tumor SUVs behaved linearly over time (∼30 to 75 min after 18F-FDG injection). Eighteen patients with breast cancer were dynamically examined with PET/CT (∼60 and 80 min after 18F-FDG injection). Maximum SUV was calculated by applying 2 different iterative reconstruction methods (high-definition reconstruction and attenuation-weighted ordered-subsets expectation maximization). Reference points for time corrections were given, and errors for corrections obtained with the reference point method were calculated. Results: Variations in the reconstruction algorithm strongly influenced the coordinates of the reference point. Time corrections using the reference point method were more accurate at higher tumor SUVs (>8 at high-definition reconstruction and >6 at attenuation-weighted ordered-subsets expectation maximization) than at lower ones. Conclusion: A common origin of tumor SUVs over time exists in breast cancer. In combination with the linear behavior of tumor SUVs between approximately 30 and 80 min, such a reference point allows for straightforward time corrections of tumor SUVs. Parameters for image reconstruction must be considered because they influence the coordinates of the reference point.