FDG dose reduction in pediatric oncology correlated with EANM procedure guidelines - A case series

Objectives Based on EANM procedure guidelines for tumor PET imaging, version 1.0 (2009), the FDG dosage can be significantly reduced in most pediatric patients (pts). In this case series, we evaluate the image quality of PET/CT scans based on criteria set by the EANM guidelines.

Methods For a 3D system with 50% overlap like ours (GeminiTF, Philips), the EANM recommends MBq/weight x min/bed > 6.9 (Product criteria 6.9). Eight pts underwent PET/CT with standard dose of 5.18 MBq/kg previously (group A), and were administered approximately 20% less activity (4.44 MBq/kg) for their subsequent PET/CT. Acquisition was 1-3 min/bed depending on body mass index, according to our institutional protocol. Two nuclear medicine physicians evaluated the image quality of each scan (1=poor; 2=borderline; 3=acceptable), blinded to information about the injected dose, and compared group A and B side-by-side. Wilcoxon test and inter-rater agreement were used.

Results Median age of 5 males & 3 females was 12 yo, range 3-19. Injected dose was 20% less in group B than group A (median 4.44 MBq/kg, range 4.07-4.81 vs. 5.55 MBq/kg, range 5.18-7.77, p<0.01). Median min/bed was 1.25, range 1-3, in group A and 1.0, range 1-3, for group B. The associated product of MBq/weight x min/bed was lower in group B than in group A (median 4.6, range 4.5-12.6 vs. 7.8, range 5.4-11.9, p=0.01). Although the product criteria 6.9 was not met in 7/8 pts, the image quality in group B was acceptable in 7/8 pts and borderline in 1/8 pts, and no study was of poor quality. Inter-rater agreement was good (weighted kappa of 0.77). Glucose level, liver SUV and min/bed were not statistically different between group A and B.

Conclusions The image quality at 20% FDG dose reduction appears comparable with those at standard dose for pediatric population. Further FDG dose reduction may be possible, and the product criteria of 6.9 may need further clinical validation