What Is PET-CT Scan? How PET-CT Works

How PET-CT Works

In this piece of content, you are going to get detailed information on how PET-CT works.

How PET-CT Works?

PET-CT scanning involves positron emission tomography (PET scanning), and computed tomography (CT) combined into one machine. 

CT stands for Computerized Tomography (commonly known as a CAT scan) and is a diagnostic medical imaging test. Like traditional x-rays, it produces multiple images or pictures of the inside of the body.

The PET scan differs from an x-ray or CT image in that it looks at the body’s metabolic activity by using a radioactive glucose injection.

Glucose is an essential molecule for almost all cells. Interestingly cancer cells have a much faster uptake of glucose in comparison with healthy cells. After injecting radioactive glucose, it accumulates mainly in cancerous areas which can be detected by a PET-CT.

Before the exam, the patient fasts for at least 6 hours. The whole procedure can last up to 2 hours.

A PET-CT scan gives information about the form and size of tumors as wells as the activity. 

What Is The Purpose Of A PET-CT?

Doctors perform PET and PET/CT scans to:

  • Make a diagnosis
    It is not always easy to differentiate benign tissue from cancer. Both can look very similar in CT. A PET can help to distinguish between them because it gives additional information like activity.
  • Finding metastases
    Metastases most commonly develop when cancer cells break away from the primary tumor. Those cancer cells can reach distant organs and lead to the growth of additional tumors. Very often, they are very small, and it is challenging for the radiologist to detect them with ultrasound, X-ray, or CT.
  • Assess the treatment
    After starting cancer treatment, the doctors may want to check if the therapy is working. A PET-CT can help to see if the tumor sizes and activity has decreased or not.
  • Cancer recurrence
    Unfortunately, even if after cancer treatment, the patient shows no sign of cancer, it can come back after years. The best way to detect cancer recurrence is to make regular checks with CT or PET-CT.
  • Evaluate prognosis
    To find the best strategy for cancer treatment, doctors need to get a full picture of the disease. Unlike an X-rax or a CT, the PET-CT scans the whole body and therefore gives a better overview.


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2. PET-CT Scan. http://www.cancercenter.com/treatments/pet-ct-scan/. Accessed 7/26/16.
3. Http://www.medscape.com/viewarticle/586604_2. Accessed 8/21/16.