PET Scan | Positron Emission Tomography Procedure | Oncology

positron emission tomography (PET scan)

What is a PET scan( positron emission tomography )?

A positron emission tomography (PET scan) scan is an imaging test that allows your doctor to detect diseases in your body. The scan uses a special colour that contains radioactive tracers. These tracers can be swallowed, inhaled, or injected into a vein in the hand, depending on the part of the body being examined. Then some organs and tissues absorb the marker.

When detected by a PET scanner, the tracers help your doctor see how well your organs and tissues are working. The marker accumulates in areas of high chemical activity, which helps because certain tissues and certain diseases of the body have high levels of chemical reactions. These areas of the disease appear as bright spots on a PET scan.

A PET scan can measure blood flow, oxygen consumption, how your body uses sugar, and much more. A positron emission tomography scan is usually a procedure for patients with PT. You can get information about your day after the test ends. In the United States, approximately 2 million PET scans are performed each year. 

How is a PET scan different from a CT or MRI scan?

PET scans show metabolic changes that occur at the cellular level in an organ or tissue. This is important because the disease often begins at the cellular level. CT scans and MRIs do not reveal problems at the cellular level.

Positron emission tomography scans can detect very early changes in your cells. CT scans and MRIs can only detect changes later because a disease changes the structure of your organs or tissues. Disease detection at the cellular level gives your doctor the best insight into complex systemic diseases, including:

  • Coronary artery disease (CAD)
  • Brain tumors
  • Memory disorders
  • Seizure errors

In many cases, a PET-CT or PET-MRI scan is possible.

Computed tomography (CT) scans use X-rays

Magnetic resonance imaging (MRI) uses magnets and radio waves. Both produce images of organs and anatomy. Positron emission tomography scans use a radioactive tracer to show how an organ is working in real-time. Positron emission tomography scans can detect cellular changes in organs and tissues prior to CT and MRI scans. Your healthcare provider can do PET and CT scans (PET-CT) at the same time. This combined test produces 3D images that allow a more accurate diagnosis.

Some hospitals now use a hybrid PET / MRI scan. This new technology creates very high contrast images and can be used primarily to diagnose and monitor soft tissue cancers (brain, head and neck, liver, and pelvis). By itself, CT scans use special x-ray equipment to create internal images of the body. Magnetic resonance imaging uses magnetic fields and radiofrequency pulses to create images of internal structures such as organs, soft tissues, and bones.

When any of these scans are combined with a PET scan, they are called image fusion. A computer combines images from two scans to create a three-dimensional image that provides more information and enables a more accurate diagnosis. These scans are not usually done to detect cancer, but some types of gallium scans are combined with newer tests, such as PET scans.

Risk factors

 There is a risk of radiation exposure.

  • For many, the benefits of a PET scan outweigh the risks.
  • However, since the PET contains radioactive material, it may not be suitable for everyone.
  • Generally, a pregnant woman should not undergo a PET scan because radioactive material can affect the fetus or baby.
  • If a woman is breastfeeding, she should follow the instructions for expressing and discarding breast milk and ask her doctor if it is safe to resume breastfeeding based on the test performed.
  • Any woman who is pregnant or breastfeeding should inform her physician directly prior to a PET scan.
  • After a PET scan, the patient is advised to stay away from pregnant women, infants, and young children for a few hours, as there is a small risk of radiation exposure.
  • Very rarely, a person may have an allergic reaction to the marker.

How do you prepare for a PET scan?

Your doctor will give you complete instructions on how to prepare for your PET. Tell your doctor about any prescription, over-the-counter (OTC), or over-the-counter medications you are taking.

You may be asked to stay away from strenuous physical activity, such as exercise, for 24 to 48 hours before the test.

The day before

Twenty-four hours before your appointment, you will be asked to follow a low-carbohydrate, sugar-free diet. Foods and drinks to avoid:

  • Grain
  • Pasta
  • Bread
  • Rice
  • Whether it’s milk and yogurt, dairy or non-dairy
  • Fruit and fruit juices
  • Alcohol
  • Caffeinated drinks
  • Confectionery products, including gum and mint
  • Foods you can eat include meat, tofu, nuts, and non-starchy vegetables.
  • If you are receiving anaesthesia for this procedure, do not eat or drink anything for the day after your PET scan. Drink only a few sips of water if you need to take any medicine.
  • If you do not have anaesthesia, avoid eating anything for six hours before the scan. Remember not to inhale gum or hard candy, cough drops, or mints.
  • You can drink water and take the recommended medications.
  • You may be asked to change into a hospital gown. Since metal can interfere with test equipment, you should also remove any jewellery you wear, including body jewellery.
  • If you are suffering from PET-CT, medical devices such as pacemakers and artificial insemination will not affect your results.
  • However, you cannot perform a PET-MRI with unlicensed medical devices or metal implants.

Medical History

You should also inform your doctor about any medical conditions:

  • If you are pregnant or think you are pregnant, tell your doctor. This test is not safe for your child.
  • If you are breastfeeding, you will need to express and store your breast milk 24 hours before the procedure; You will not be able to breastfeed for 24 hours after the test.
  • If you have diabetes, you will receive special instructions for preparing for the test because the previous fasting can affect your blood sugar levels. You may be told to take your usual dose of insulin and eat a light meal 4 hours before the scan.

How is a PET scan performed?

Before scanning, you can get tracers through the vein in your hand, through the solution you drink, or the gas you inhale. Your body needs time to absorb the markers, so you must wait an hour before the scan can begin.

  • The time it takes your body to fully absorb the marker depends on the area of ​​the body being scanned.
  • While you wait, you want to limit any movement, relax, and try to keep warm. If you have a brain scan, you may want to avoid television, music, and reading.
  • You will then have a scan, which will last 30 to 45 minutes. You are lying on a narrow table connected to a PET machine, which is “O”. It looks like a capital letter. The table slides slowly into the machine in order to perform the scan.
  • You still need to lie down while you can. The technician will let you know when to be consistent. You may be asked to hold your breath for several seconds. During the test, you may hear popping and clicking sounds.
  • When all the required images are recorded, it exits the machine. Then the test is complete.

What happens after a PET scan?

 After the test, you can find out how your day was if your doctor doesn’t give you other instructions.

  • However, since radioactive material stays in your body for about 12 hours, you may want to limit your contact with pregnant women and babies during this time.
  • Drink plenty of fluids after the test to flush the markers out of your system. Generally, all tracers leave your body after two days.
  • Meanwhile, the trained specialist will understand the images from the PET scan and share the information with your doctor. The results are usually ready for your doctor within two business days, and your doctor will receive the results with you at your next appointment. 

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