May 12, 2015
The radiolabelled glucose analogue, 18F-fluoro-deoxyglucose (FDG) is widely used in the diagnosis and staging of cancer. FDG becomes concentrated in cancer cells due to their increased need for glucose and can be visualised using positron emission tomography (PET) imaging. In addition to highlighting the presence and location of a tumour, the intensity of the signal provides an indication of how aggressive and fast-growing it is.
PET scans are conducted in fasting patients so that the signal is not diluted by unlabelled glucose and because other cells generally do not use glucose in the fasting state. However, since it is not practical to conduct numerous PET scans over a long period, only one image is obtained at the point equilibrium is reached. This means that only tracer uptake and not tracer availability can be measured. The latter is usually considered to be relatively similar between patients and is therefore ignored.