Optimization of SUV with Changing the Dose Amount in F18-FDG PET/CT of Pediatric Lymphoma Patients.

Aims: We aim to reveal an effect of residual activity leftover within the medical materials other than the empty syringe used for injection of the tracer on SUV measurements and consequently effect on possible treatment response assessment.

Background: Staging and follow-up of pediatric lymphoma patients mainly achieved by the help of PET/CT scans. It is crucial to make an optimal imaging technique for interpreting individual images and assessing treatment response.

Objective: Standardized uptake value measurement is an important quantification parameter in PET/CT scanning of childhood lymphomas. Low dose of activity used in pediatric oncology patients makes them vulnerable to small changes of input values for subsequent metabolic parameters.

Methods: Sixty-eight pediatric lymphoma patients below 50 kg were included into the study. SUVmax, SUVpeak values of the most metabolically active lesions, along with liver and mediastinum, were recorded. Metabolic parameters of the lesions/lymph nodes, mediastinum and liver parenchyma were compared before and after counts from medical materials other than empty syringe were taken into account. Wilcoxon signed-rank test was used for non-parametric paired sampled tests for the groups.

Results: There were statistically significant differences between the whole 6 above-mentioned groups confirming the importance of residual counts on metabolic parameters (p < 0.001).

Conclusion: Our study demonstrated residual radioactivity in medical materials such as serum line tubes, i.v. catheters, three-way stopcock and also butterfly needles used during intravenous injection should also be included for optimum quantitative metabolic parameter values and to minimize its the adverse effect on treatment response evaluation, especially in borderline lesions.