Assessment of Uptake Times in PET/CT.

Introduction: Positron emission tomography-computed tomography scans (PET/CT) are an important diagnostic tool that work by revealing the physiologic function of tissues within the body. An uptake time within recommended limits is vital in ensuring images are of utmost quality and standardized for interpretation reproducibility. According to the SNMMI Procedure Standard for Tumor Imaging with ¹⁸F-FDG PET/CT 1.0, uptake times should be constant whenever possible, though should be obtained at least 45 minutes after radiopharmaceutical injection. Many other FDA approved radiopharmaceuticals, including ⁶⁸Ga-PSMA-11, ⁶⁴Cu-Dotatate, and ¹⁸F-DCFPyL, have uptake ranges that include 60 minutes as acceptable according to package insert. The objective of this study was to retrospectively determine clinical PET/CT uptake times at Northwestern Memorial Hospital.

Methods: Using Visage imaging software, 198 consecutive PET/CT studies that were completed between June 1^st to June 15^th of 2022 were analyzed. Factors of analysis include type of scan, injection time, scan start time, and the uptake time for each study. Calculations were performed in order to determine average uptake time and standard deviation for further discussion.

Results: The average uptake time for PET/CT studies at Northwestern Memorial Hospital was calculated to be 65.6 minutes, with a range of 44.5 to 105.7 minutes (see Graph 1). The standard deviation of the calculated uptake times was 11.3 minutes.

Conclusions: Upon review of the results, although the average uptake time is 65.6, the standard deviation has been deemed large enough to warrant a change in department uptake time strategy.

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