Surgical removal is the treatment for many different cancers. Patient outcomes depend on complete cancer removal with no tumour present at the edge of the section removed (specimen). If cancer is left behind, then patients might need additional cancer treatment. Regardless of whether extra treatment is required, knowing that removal was incomplete causes anxiety. The need for a wide removal of the tumour must be balanced against the harm caused by more extensive surgery particularly when important organs and structures are close by. The fact that the cancer is not visible to the surgeon during the operation means that there is an element of guesswork when deciding how much tissue to remove. This study is examining a technique that the investigators hope will provide surgeons with more precise information about how much tissue to remove during cancer operations using a new type of Positron Emission Tomography-Computed Tomography (PET-CT) scanner. Patients with different types of cancer (e.g. prostate, head and neck cancer) will be injected with a small amount of radioactive tracer at the beginning of their cancer operation. This tracer will attach itself to the cancer cells. Once the surgical specimen is removed it will be placed into the specimen PET-CT scanner so that the surgeon can see the cancer within the specimen. The investigators will then compare the results of the scan of the specimen taken during the operation with the results when the whole specimen has been examined under the microscope. Examination under the microscope is considered to be the gold standard for deciding whether the cancer removal operation has been successful. This study aims to tell us how accurate the new specimen PET-CT scanner results are, and so whether or not surgeons can rely on the results to guide them during operations in the future.

Inclusion Criteria:

For prostate cancer patients:

1. At least 18 years old at time of consent.
2. Listed for Robotic Radical Prostatectomy.

For head and neck cancer patients:

1. At least 18 years old at time of consent.
2. Listed for resection of oral squamous cell carcinoma head and neck cancer resection.
3. Specimen able to fit into Xeos Aura specimen container.

Exclusion Criteria:

For prostate cancer patients:

1. General or local contra-indications for resectional surgery.
2. Lacks capacity to provide informed consent.
3. Currently participating in another interventional research study that in the judgment of the investigator would negatively affect the participant and/or this study's data integrity.

For head and neck cancer patients:

1. General or local contra-indications for resectional surgery.
2. Lacks capacity to provide informed consent.
3. Pregnant or breast feeding patient.
4. Currently participating in another interventional research study that in the judgment of the investigator would negatively affect the participant and/or this study's data integrity.