Figure 4. Specificity of [¹⁸F]PARPi tumor uptake was confirmed by blocking with Olaparib.

In vivo PET/CT imaging and quantification of [¹⁸F]PARPi in juvenile brainstem tumor-bearing mice (ntv-a/p53^fl/fl mice injected with transfected DF1 cells RCAS-PDGFB and RCAS-Cre in the brainstem at 2–4 days of age). [¹⁸F]PARPi was intravenously injected in tumor-bearing (DIPG) or healthy mice (control); to control for specificity, 1 mg olaparib was injected 30 min prior to [¹⁸F]PARPi (Block) to occupy specific binding sites (n=3/group). After imaging, intracardiac perfusion with 4% PFA was carried out and brains were conserved for histology. (a) Representative PET/CT images of the brainstem region compared to H&E and PARP1 staining of the same animals. (b) Quantification of %ID/g of the entire brain was derived from the PET/CT data set using the CT as reference for creating VOIs. (c) Similarly, the %ID/g was analyzed for the brainstem region using the CT as reference for creating VOIs. Statistical significance was determined using an unpaired student’s t-test assuming equal SD. White arrow points at tumor location.