PET/CT explained

History

 

The idea of positron emission imaging is not new; this technology was first used in the clinical setting in the 1950s. During the 1960s, the earlier version of positron emission tomography (PET) was developed. It was not until this century that the hybrid system of combining a positron emission tomography (PET) with a computed tomography (CT) was available commercially as a PET/CT scanner.

 

Tracer injections

 

To perform a PET scan, a very short lived radioactive tracer is first injected into a patient, commonly in the form of radioactive glucose (18F-labelled fluoro-deoxyglucose or FDG). The amount of tracer administered is very small, in the range of nanograms. After injection, the patient will rest for 60 to 90 minutes allowing time for the tracer to be metabolised in the body. It was found that most cancer cells have a higher glucose uptake than the adjacent healthy cells. With this information in mind, the cancer and its metabolic activity can be easily identified on the images. 

 

 

Combining a PET scanner with a Computer Tomography (CT) scanner

 

PET images do not give good anatomical detail which is required for treatment planning. The combination of a PET scanner with a Computer Tomography scanner compensated for this by allowing anatomical images to be obtained at the same time, thus allowing the co registration of both sets of images. Computed tomography uses multiple x-rays to generate a three dimensional image. Images obtained in this way show exquisite anatomical detail.

Combining these two technologies, the PET/CT will be able to provide us with information on where the cancer is and its relationship with the adjacent healthy tissue. We are also able to identify any distant spread of the cancer much earlier than any other imaging methods.

 

 

 

Cardiology and neurology diagnostics

 

PET/CT has other clinical uses than just cancer imaging. It can look at the elevated glucose metabolism in inflammatory cells in arterial walls (Arteritis). This imaging can also determine blood flow to the heart muscle and therefore the effects of a myocardial infarction on areas of the heart. PET/CT can assist in areas of Epilepsy, Alzheimer's disease and other neurology diseases.

 

 

Equipment at Addenbrooke's

 

GE DiscoveryTM 690 PET/CT system - a 64 slice PET/CT scanner with time-of-flight technology. The scanner is located in a purpose built spacious unit. This unit is fully equipped to allow an extensive PET/CT service. We have the ability to provide PET/CT with diagnostic contrast enhanced CT and PET/CT with radiotherapy planning. Facilities are available to provide cardiac and paediatric imaging.

A close collaboration has been formed with the Wolfson Brain Imaging Radiochemistry Department within Addenbrooke’s Hospital to supply radiopharmaceuticals for both clinical and research purposes. The Wolfson Brain Imaging Department has a cyclotron which produces a wide range of positron emitting tracers including F-18 and C-11 which are used in manufacturing PET/CT tracers.

 

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