Measurement of ¹⁸F-FDG concentrations in blood samples: Comparison of direct calibration and standard solution methods

Objective: The purpose of this study was to compare the accuracy and reliability of 2 well counter methods for measuring the activity concentration of ¹⁸F-FDG in blood samples. Methods: Three to 5 blood samples from 154 patient studies were weighed and measured in a well counter. The ¹⁸F-FDG activity concentration was derived using, first, a direct calibration factor to convert measured well counter readings into activity concentration and, second, a comparison of measured counts with those of a specified standard solution. Results: The ratio between the activity concentration results of the 2 methods was 0.996 ± 0.033, indicating that the methods provided equal results. Conclusion: Because the standard solution method is more prone to human error, less reproducible, and more labor intensive, preference should be given to the direct calibration method.