Background: Oncologic PET/CT studies require a prescribed 18F-fluorodeoxyglucose (FDG) dose delivered as a bolus prior to imaging; this same dose is used in the standardized uptake value (SUV) calculation. An infiltration is the misadministration of FDG outside the systemic circulation and will result in underestimating the SUV. Interpreting and treating physicians are often unaware of infiltrations when the injection site is outside the imaging field of view. Despite existing quality control (QC) efforts to ensure accuracy of the administered dose, there is no routine QC method that confirms complete delivery of the dose into the patient's circulation. 5 technologists in our center participated in a quality improvement project that reduced infiltration rates from 13.3% to 2.9% (P-value for difference in rates <.0001). Our objective was to evaluate sustainability of the improvement. Methods: 8 new technologists joined the team during the sustainability period. Infiltration rates in the sustainability period were calculated, controlling for technologist- and patient-level correlations (SAS v. 9.4). Infiltration rates were compared between QI participants and nonparticipants. Results: 13 technologists administered 1,240 injections in the sustainability period (10/7/2017–9/26/2018) with a 3.1% infiltration rate. The Infiltration rate for technologists who did not participate in the QI project was higher (6.08%; SE: 1.31%; 95% CI: 3.19%–8.97%) compared to the QI project technologists (2.05%; SE: 0.0055%; 95% CI: 0.83%–3.26%). This 66% decrease in rates was found to be statistically significant (P=.017). Conclusions: Although the overall infiltration rate remained low in the sustainability period, rates among new technologists who joined after the QI project were higher, compared to their QI project counterparts. This is especially important given the number of new technologists (n=8) compared to the QI project technologists (n=5). Quality improvement is a continuous process, and dissemination of lessons learned from the QI project should be provided as new technologists are onboarded. Because proper injections are critical to PET/CT images, ongoing monitoring is essential to ensuring that injection quality remains high, as infiltration rates can change over time.