PET-CT has revolutionised medical diagnosis in many fields, by adding precision of anatomic localisation to functional imaging, which was previously lacking from pure PET imaging. For example, in oncology, surgical planning, radiation therapy and cancer staging have been changing rapidly under the influence of PET-CT availability, to the extent that many diagnostic imaging procedures and centres have been gradually abandoning conventional PET devices and substituting them with PET-CTs. Although the combined/hybrid device is considerably more expensive, it has the advantage of providing both functions as stand-alone examinations, being, in fact, two devices in one.
Before carrying out a PET scan, a radioactive medicine is produced in a cyclotron. The radioactive medicine is then tagged to a natural chemical. This natural chemical could be glucose, water, or ammonia. The tagged natural chemical is known as a radiotracer. The radiotracer is then inserted into the human body.
Once the radiotracer is inside the human body it will reach the areas inside the body that use natural chemical. For example, FDG (fluorodeoxyglucose - a radioactive drug) is tagged to glucose to make a radiotracer. The glucose goes into those parts of the body that use glucose for energy. Cancers, for example, use glucose differently from normal tissue - so, FDG can show up cancers.
The following are considered to be the biggest advantages of a PET CT Scan:
A powerful source of data to help make the right decisions
Helps to avoid a number of invasive procedures
Can help avoid unnecessary surgery
Can tell whether a tumour is benign or cancerous
Can show all the organ systems of the body in a single exam, showing, for example, whether cancer has spread
Detects the disease, often, before it shows up on other tests
Is an early predictor of the patient’s response to therapy