A fluorine-containing version of glucose, Fluorodeoxyglucose or FDG, is the radioactive tracer most commonly used. A 'tracer' is a radioactive substance given in extremely small quantities, so that it should not have any chemical or biochemical effect. The technique is sometimes called FDG-PET to distiguish it from PET imaging with other tracers.

FDG is a useful tracer because tumour cells often use glucose for energy metabolism more actively than normal cells. After injection of FDG, the patient is allowed to rest quietly for one hour before PET imaging. The images then help to show whether primary or metastatic tumours are present.

In some cases, FDG-PET may also be useful in evaluating whether a cancer treatment is working or in helping to define the size and position of the tumour, so that radiotherapy can hit the required target and minimise damage to normal tissues.

For research purposes, other PET tracers are being developed. These can take advantage of other disturbed features of tumour cell metabolism:

• Fluorothymidine (FLT) probes increased uptake of raw materials for making DNA
• Fluorethyltyrosine (FET) can be used to monitor increased protein sysnthesis
• radioactive versions of new drugs may be used to test how well the drug is taken into cancer cells

Further information

Find out more about our research in this area:

• clinical trials
• radiotherapy planning
• paediatric cancer