In head and neck cancer, areas of tumours with low oxygen supply (called tumour hypoxia) harbour cells that are resistant to radiation and are prone to metastasize. Modern radiotherapy techniques are precise enough to deliver radiation to these small areas and could be used to target these areas to receive higher doses of radiation than the rest of the tumour to overcome resistance. Hypoxia can be "seen" in the body using special imaging such as [F-18]-FAZA-PET ([F-18]-Fluoroazomycin arabinoside positron emission tomography) but it has not been tested as a method for creating radiation treatment targets. As part of regular pathology tumour tissue is sliced extremely thinly (<1/100th of a millimeter) and stained so that individual cells can be seen under a microscope. Immunohistochemistry (IHC) is a special type of "stain" that can specifically highlight hypoxic areas. This method is considered the most accurate way to inspect for the presence of hypoxia. There is not a specific staining target for hypoxia ordinarily, but when patients ingest a substance called pimonidazole-HCl it builds up specifically in hypoxic areas and can be targeted for IHC staining. In this study participants with oral tongue cancer will have a [F-18]-FAZA-PET scan and take a single dose of oral pimonidazole-HCl before having surgery to remove their cancer. The whole tumour will be used to create microscope slides using very thin slices of the tumour. The slices will be stained using IHC to show where the pimonidazole has built up and digital scans of the slides will be made. The hypoxia seen on the FAZA-PET scan will be "matched" with hypoxia on the electronic slides to see if the FAZA truly shows where hypoxia is in tumours and if it could be used as a way to plan radiation treatments to deliver more radiation to just those areas.