Where are we with imaging oxygenation in human tumours?

Tumour hypoxia represents a significant challenge to the curability of human tumours leading to treatment resistance and enhanced tumour regression. Tumour hypoxia can be detected by non-invasive techniques but the inter-relationship between these techniques needs to be better defined. [(18)F]Fluoromisonidazole ((18)F-MISO) and Cu-labelled diacetyl-bis(N(4)-methylthiosemicarbazone (Cu-ATSM) PET, and blood oxygen level-dependent (BOLD) MRI are the lead contenders for human application based on their non-invasive nature, ease of use and robustness, measurement of hypoxia status, validity, ability to demonstrate heterogeneity and general availability; these techniques are the primary focus of this editorial.