18F-FDG PET standard uptake values of the normal pons in children: establishing a reference value for diffuse intrinsic pontine glioma

Background: Positron emission tomography (PET) scanning with [F-18]fluorodeoxyglucose (F-18-FDG) is a useful diagnostic and prediction tool in brain tumors, but its value in childhood diffuse intrinsic pontine glioma (DIPG) is still unclear. For interpretation of F-18-FDG PET results in DIPG, uptake values of the normal pons of children of increasing ages are mandatory. The aim of this study was to determine F-18-FDG standard uptake value ratios (SUVr) of the normal pons and to compare these to those of DIPG. Methods: We studied 36 subjects with a normal, non-affected pons (aged 5 to 23 years) and 6 patients with DIPG (aged 4 to 17 years) who underwent F-18-FDG PET scanning. Magnetic resonance imaging (MRI) was co-registered to define the regions of interest. SUVr and SUVrmax for the pons/cerebellum (SUVr(p/c)) and the pons/occipital lobe (SUVr(p/o)) were calculated. Independent-samples t tests and Mann-Whitney U tests were used to compare the mean SUVr and Pearson's test for correlations. Results: For the normal pons, mean SUVr(p/c) and SUVr(p/o) were 0.65 (+/- 0.054) and 0.51 (+/- 0.056), respectively. No significant correlations were found between the SUVr of the normal pons and sex, age, nor pontine volume. A modest but statistically significant correlation was found between SUVr and post-injection time acquisition timing. For DIPG, mean SUVr(p/c) and SUVr(p/o) were 0.74 (+/- 0.20) and 0.65 (+/- 0.30), respectively, while mean SUVr(p(max)/c) and SUVr(p(max)/o) were 1.95 (+/- 0.48) and 1.81 (+/- 0.20), respectively. Conclusion: The SUVr of the unaffected pons are strikingly constant between children, irrespective of sex and age, and can therefore be well used as a reference value for F-18-FDG PET studies in DIPG.