PARP1 and neoplasm: [18F]Olaparib tumour uptake could be blocked by co-administration of an excess of unlabelled olaparib in either tumour model (from 6.1 ± 0.5%ID/g and 7.4 ± 0.9%ID/g to 1.2 ± 0.3%ID/g and 1.2 ± 0.2%ID/g, in U251MG and U87MG xenografts, respectively; P < 0.001), and their PARP expressing organs, such as spleen, pancreases and liver, indicating selective uptake.