PETCT (Positron Emission Tomography Computerised Tomography) is a detailed scan combining a normal Computed Tomography (CT) scan with a Positron Emission Tomography (PET) scan. It is performed on the same scanner all in one appointment.


What does it involve?

The CT scan uses x-rays to obtain an image of the body. The PET involves a small injection of radioactive tracer which travels through the body and is detected by the scanner.

Different tracers, called radiopharmaceuticals, will localise in different diseases or conditions and provide detailed information on the internal anatomy and function of the body. The two scans are then fused together to create a combined anatomical and functional image of the inside of the body.

This enables the consultant to more accurately diagnose and develop an individualised treatment plan for each patient.

The radiation used is safe and kept very low and there are no side effects or lasting effects after the scan.



PETCT scan is an outpatient procedure and can be performed to:

  • Detect cancer
  • Determine whether a cancer has spread in the body
  • Assess the effectiveness of a treatment plan, such as chemotherapy or radiotherapy
  • Determine if a cancer has returned after treatment
  • Evaluate brain abnormalities, such as tumours, memory disorders, seizures and other central nervous system disorders
  • Detect areas of infection or inflammation


On the day:

On the day of your PETCT appointment, you will be given an injection of the radioactive tracer. You will then be asked to relax in one of our chairs to allow the tracer to travel through your body. This “uptake period” allows time for the tracer to work is between 60 to 90 minutes. You are able to read, listen to music or use any smart devices you bring with you during this time.

This time allows the radiotracer to travel through the body and to be absorbed by the organ or tissue being investigated.

You will then be given a chance to use the bathroom before going onto the PETCT scanner and the imaging will begin. The CT scan will be carried out first, followed by the PET scan. The scan itself usually takes 20-30 minutes. The whole process will take approximately 2 hours.


For more information on PECT and how to prepare for your appointment, please see the ‘Patient Information Leaflet’ in the right-hand column


Cancer Centre London

Parkside Hospital

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