[Aim] To compared the usefulness of [F-18]choline and [F-18]FDG in monitoring brain tumor growth and the therapeutic effect of gold-198 nanoparticles ([Au-198]GNP) intratumoral injection in rats. [Materials and Methods] Brain tumor cells (C6 glioblastoma) were injected into the brain of 8 rats at 4-8 weeks old and allowed brain tumors growth for 2 weeks before [Au-198]GNP intratumoral injection for therapy. The [F-18]choline and [F-18]FDG micro-PET/CT imaging (Tri-Modality FLEX Triumph™ Imaging System, Gamma Medica-Ideas, Northridge, CA) were performed at 12 days ([F-18]choline n=4, [F-18]FDG n=4) and 13 days ([F-18]choline n=4, [F-18]FDG n=4) after 10^6 tumor cell injection, respectively. Three rats received [Au-198]GNP intratumoral injection therapy and other 4 allowed continuously tumor growth for one week. All 7 rats had follow-up [F-18]choline and [F-18]FDG micro-PET/CT imaging at 20 and 21 days after tumor injection. The mean standard uptake values from regions of interest over the tumor and background were obtained for tumor-to-background (T/N) ratios analysis. The mean and standard deviation (SD) of T/N ratios of [F-18]choline and [F-18]FDG were calculated. [Results] The T/N ratios (mean±SD, n=8) of [F-18]choline and [F-18]FDG at 12/13 days after tumor injection were 6.71±1.05 and 1.87±0.28. The T/N ratios of [F-18]choline and [F-18]FDG at 20/21 days with [Au-198]GNP intratumoral therapy (n=3) were 6.00±0.05 and 2.02±0.56. Those 4 rats without [Au-198]GNP therapy, the T/N ratios of [F-18]choline and [F-18]FDG at 20/21 days were 7.60±0.74 and 2.42±1.11. The T/N ratios of both [F-18]choline and [F-18]FDG increased from 12 days to 20 days of tumor growth in 4 rats. However, the T/N ratios decreased in all 3 rats after [Au-198]GNP intratumoral injection therapy as compare with those of no [Au-198]GNP therapy. [Discussion and Conclusion] The intratumoral injection therapeutic effect of [Au-198]GNP in rat brain tumor can be observed by using both [F-18]choline and [F-18]FDG. The [F-18]choline imaging revealed low normal brain cortical background, therefore higher T/N ratios than those of [F-18]FDG. The [F-18]FDG might be affected by normal cortical brain activity as well as [Au-198]GNP induced inflammatory reaction around intratumoral injection sites. The limitation of this study includes no pathology results to confirm the therapy effect. However, the [Au-198]GNP intratumoral radiotherapy effect has been proved and published in a previous work from this group .
Date:
2014-10
Relation:
European Journal of Nuclear Medicine and Molecular Imaging. 2014 Oct;41(Suppl. 2):S392.
