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.

UNLABELLED 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.