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PET Scan: Why is it Needed and How is it Done?

PET Scan: Why is it Needed and How is it Done?

A PET scan is short for positron emission tomography test. This technology is used to check how well your tissues and organs are functioning at the cellular level. A PET scan requires a radiotracer that is either injected into your body or given through a pill. These are then naturally absorbed by the body.

To get the imaging after placing the radiotracer in your body, you are then made to lie down in a ring-shaped or tunnel-like device. This scanning device catches the emitted radiation and shows in images where issues in your body may lie. These can occur in the form of small dots on areas where diseases can be pre-setting. A PET scan is most commonly done to diagnose diseases such as cancer, cardiovascular problems, and brain disorders.

A PET scan is also able to measure blood flow, oxygen use, and blood sugar optimization.

Why is a PET Scan done?

Since a PET scan is used to detect underlying conditions in the body, it is mostly recommended by doctors when they see a disease surfacing or to evaluate an ongoing treatment. This means that the scan can be used to diagnose cancer, heart diseases, or brain disorders such as Alzheimer’s.

If you have cancer or possible signs, your doctor will:

  1. Look for the organ or body part it is in
  2. See how far spread is the cancer
  3. Check if your existing cancer treatment like chemotherapy or radiotherapy is working
  4. Evaluate if cancer has become immune to the treatment

If you have heart disease, your doctor is most likely to:

  1. Examine the blood flowing to your heart
  2. See how affected your heart is
  3. Decide a treatment on the basis of your PET scan
  4. See if there are any pre or post requisites of a heart attack

If your doctor is checking for brain disorders or conditions, he or she is to look for the following issues:

  1. Tumors
  2. Stroke
  3. Seizures
  4. Alzheimer’s disease
  5. Parkinson’s disease

Prerequisites of a PET Scan

The prerequisites for a PET scan can sometimes depend on the condition your doctor is trying to look for. Because of this, you can be asked to refrain from certain activities such as vigorous exercise or any other physical activity.

The day before your PET scan, you will be asked to stick to a lighter diet that does not contain carbohydrates and sugar. This is because PET scans evaluate blood sugar optimization in the body. If you consume a heavy diet prior to your test, it can show ineffective results during your PET scan.

You should ideally avoid the following food products or groups:

  1. Cereals
  2. Pasta or pizzas
  3. Processed bread
  4. Alcohol
  5. Caffeinated beverages
  6. Dairy products
  7. Fruits

Remember to keep your meals light and without fried foods. This will ensure that your test result is optimal and not misleading.

You will be asked to change into a gown and take off any metallic jewelry. Please keep in mind to do so. If you have any metal implants such as a DBS wire in the brain, ask your doctor about its effect on the scan.

PET scan may be unsafe for fetus, hence if you’re pregnant, let your doctor know. If you’re in the breastfeeding phase, you may be required to pump milk 24 hours before the procedure. Also, you cannot breastfeed 24 hours after the scan either. So make arrangements accordingly.

Understanding the Results of your PET ScanPET scan

PET scan results usually arrive within 24 to 48 hours after the test is done. A radiologist will look at your results to interpret how your organs and tissues are performing. A PET scan has pictures with bright spots due to the radioactive tracers that were inserted into your body.

These spots display the chemical activity in your organs and tissues and hence will show the radiologist where the issue really lies.

If the result is normal, then the scan will show no abnormalities in the position, shape, or size of the organ. If the result shows irregularities in the mentioned characteristics of the organ, then it may signify disease or other conditions. However, please note that your doctor will order other tests such as an MRI or CT to arrive at a conclusion.

When should a PET scan be repeated?

If you have been diagnosed with a disease like cancer or cardiovascular disease, during the progression of your treatment, you may be asked to repeat the test. There is no set timeline for repeating a PET scan.

In any case, your doctors, diagnostics, and other experts will let you know about the need for new body scans. If you’re undergoing heavy treatment and wish to get tested, do not do so without asking your doctor.

PET Scan Procedure

The procedure of the test is as follows:

  1. As mentioned above, you will be asked to eat a lighter meal the day before and nothing on the morning of the test. If you are on medication or treatment that requires you to eat something, ask your doctor first.
  2. The reason why carbohydrates are restricted is for the even distribution of radiotracers in the body. This can get hampered if your blood sugar levels are high.
  3. A PET scan takes 45 minutes to 90 minutes, depending on the aim of the procedure and what the doctors deem fit. It will take 30 minutes to one hour for the radiotracer, either by injection or a pill, to settle and spread in the body.
  4. You will be asked to wear a gown and remove any metals from your body as they can come in the way of your PET scan. If you have a pacemaker instilled in your body, inform your diagnostic technician right away.
  5. A PET scan machine is a large doughnut-like piece of equipment that has a bed on which you lie down. If you have claustrophobia, ask your doctor about the best way forward. You will be required to remain extremely still while the procedure is on.
  6. This procedure is painless and you will hear the machine clicking images. Doctors prescribe drinking plenty of fluids like water and juices after the test to get the radiotracer out of your body.

Learn more about medical diagnostic tests here.

Hello Health Group does not provide medical advice, diagnosis or treatment.

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Written by Kristel Lagorza Updated Jan 25
Fact Checked by Hello Doctor Medical Panel