What is PET/CT?

PET/CT is an imaging method which is created by combining PET (Positron Emission Tomography) and CT (Computerized Tomography) devices, providing an opportunity to obtain metabolic and anatomical information about organs.

Positron emission tomography (PET) is an imaging test which helps revealing how your tissues and organs function. PET scan uses a radioactive medicine (tracer) to display this activity

This tracer can be injected, swallowed or inhaled depending on the organ and tissue, to be examined. The tracer accumulates in the body areas which have high level of chemical activity, frequently corresponding to the disease areas. In a PET scan, these areas are seen as bright points.

PET CT scan is beneficial in revealing or evaluating various diseases, including some cancers, heart diseases and brain disorders.

Why is PET/CT Scan made?

PET scan is an effective way of examining the chemical activity in body parts. It can be beneficial in revealing or evaluating various diseases, including some cancers, heart diseases and brain disorders. The images, which are obtained from PET scan, provide different information from other scanning methods like computerized tomography (CT) or magnetic resonance imaging (MRG). A PET scan or combined CT-PET scan allows your physician to make the diagnosis of your disease better.


As cancer cells have higher metabolic rate than normal cells, they are seen as bright points in PET scans. PET scans can be helpful for the following:

  • Diagnosis of cancer
  • Revealing if your cancer is spreading or not
  • Checking if a cancer treatment works or not
  • Determination of the recurrence of cancer

PET scans must be carefully interpreted because many non-cancerous diseases can be seen as cancer and many cancer types are not seen in PET scans. The cancer types which are very likely to be seen in PET scans include the following:

  • Brain Tumor
  • Breast Cancer
  • Cervix – Cervical Cancer
  • Colorectal Cancer
  • Esophagus Cancer
  • Head and Neck Cancer
  • Lung Cancer
  • Lymphoma
  • Melanoma
  • Pancreas Cancer
  • Prostate Cancer
  • Thyroid Cancer

Heart disease

PET scans can display the areas where blood flow decreases in heart: This information can help you and your physician decide whether you can benefit from an operation to open a heart artery, suffering from thromboembolism (angioplasty), or coronary artery bypass surgery.

Brain disorders

PET scans can be used for the determination of specific brain disorders similar to the following:

  • Tumors
  • Alzheimer disease
  • Seizures

What are the benefits and risks of PET/CT?


  • Nuclear medicine examinations can provide unique information which cannot be obtained with other imaging methods frequently, including information which is related to both function and anatomical structure of body.
  • Nuclear medicine examinations give the most beneficial information in order to diagnose many diseases and determine the convenient treatment, if available.
  • Nuclear medicine has a lower cost than surgical exploration and can provide more certain information.
  • Nuclear medicine provides the potential of determining a disease at an early stage often before the signs occur or the abnormalities are diagnosed by other diagnostic tests.
  • PET scans can eliminate the need of surgical biopsy or identify the best biopsy location by determining if lesions are benign or malign.
  • PET scans can also provide additional information which is used in planning radiation therapy.


In your PET scan, a radioactive medicine (tracer) will be administered to your body. The amount of radiation which you will be exposed to has a small risk of negative impact. However, this tracer:

  • Can cause major allergic reaction in rare situations.
  • Can expose your unborn baby to radiation, if you are pregnant.
  • Can expose your child to radiation, if you are breast feeding.

Consult your physician about the benefits and risks of PET scan.

How will you be prepared?

Inform your physician about the following:

  • If you have experienced any negative allergic reaction at any time
  • If you have been ill recently or had a medical disease like diabetes
  • If you are taking medicine, vitamin or herbal supplement
  • If you are pregnant or you have suspicions
  • If you are breast feeding
  • If you are afraid of confined spaces (claustrophobia)

Your physician will provide your detailed information about the preparation for the scanning process. The basic rule is that you should avoid doing heavy exercise few days before and stop eating few hours before the scan.

What should you expect?

PET scanner is a big machine, similar to computerized tomography (CT) machine, standing vertically and looking like a gigantic donut. This operation, which can be made in outpatient settings, takes approximately two hours (you do not need to stay at the hospital for a night). When you present for scan, the following can be asked from you:

  • Put on your hospital clothes
  • Empty your bladder

Then, a radioactive medicine (tracer) will be given to you. Depending on the type of tracer, to be used, the medicine can be injected to your body or you can be asked to inhale or swallow. If the medicine is injected, you may feel coldness moving up your arm for a short time. You will need to wait between 30 and 60 minutes to let your body absorb the tracer.

During PET scan

When you are ready, you will lie on a slippery, narrow, filled table, sliding into the scanner. During scan, you will need to stay as motionless as possible in order to not make the images blurred. It takes 30 minutes to complete the test. The machine makes humming and chattering sounds.

The test does not cause any pain. If you are afraid of confined spaces, you may feel anxiety while being inside the scanner. Ensure that you report any problem that you have to the nurse or the technician. A drug can be given to you to help you get relaxed.

In some cases, CT and PET can be scanned in the same machine at the same appointment. Firstly, CT will be scanned and it will take almost 10 minutes.

After PET scan

After the examination, you can continue to your ordinary daily routine, unless your physician states otherwise. It will be necessary to drink a lot of water to help the tracer drain away from your body.

Who does interpret the results and how can I take them?

Another physician, who has taken a specialist training on radiology or nuclear medicine, will interpret the images and send the report to the physician who referred you.


In the images of PET scan, bright points are seen in the places where the radioactive tracer is accumulated. These points reveal the high level of chemical activity and how your tissues and organs function. A physician, who received a specialist training to interpret scan images (radiologist), will report the findings to your physician.

The radiologist will also compare the PET images with the ones of recently performed examinations, such as computerized tomography (CT) or magnetic resonance imaging (MRI). Or these images can be combined in order to provide more detailed information about your disease.

What are the areas of use for PET/CT?

  • It is used in the diagnosis of cancer types, which show sensitivity to the used radioactive material, in primary staging, in the evaluation of the given response to a treatment and in the steps of re-staging,
  • In the examination of living tissue before bypass and stent in selected heart patients,
  • Differential diagnosis of Alzheimer in neurology and determination of the focus of a planned surgical operation for epilepsy patients.

Advantages of PET/CT

PET/CT allows distinguish benign/malign lesions.

It prevents unnecessary biopsy and surgical operations.

With only a single examination, it allows determining the spread of cancer in vitro, meaning its stage.

It is the method with highest accuracy in the detection of cancer recurrence.

In some cancer types, it allows evaluating the sensitivity to chemotherapy medicine. Therefore, it allows changing an ineffective treatment with an effective one.

After radiotherapy and chemotherapy treatments, it allows the evaluation of patient’s response to the treatment.

What are the preliminary preparations for patients before examination?

Patients are expected to be fasting for at least 6 and ideally 12 hours.

For the diabetic patients, the treatment is required not to be ceased and blood sugar of the examination day must be under 200 mg/dl.

Beginning 1-2 hours before patient’s appointment, it is advised to drink minimum 2 liters of water.

How is imaging made in PET/CT?

The used radioactive material is injected intravenously.

After the injection, the patient completely rests in special rooms for 60 minutes.

At the end of this resting period, the scan process begins.

Scan area is an area which is located between skull base and upper part of femur.

Depending on the patient’s height, the scan duration can change between 15 and 30 minutes.

Ask Your Doctor a QuestIon