Here, we used [18F]olaparib, a PARP-targeted PET imaging agent which previously demonstrated successful imaging of PARP in human PDAC xenograft models [6], to investigate the effects of injected mass (μg) and molar activity of [18F]olaparib on tumour uptake and target expression in glioblastoma mouse models. The gene discussed is PARP1; the disease is glioblastoma.