Positron Emission Tomography PET – Indications, Procedures, Results

A positron emission tomography scan is a type of imaging test. It uses a radioactive substance called a tracer to look for disease in the body.

A positron emission tomography (PET) scan shows how organs and tissues are working.

  • This is different than MRI and CT scans. These tests show the structure of, and blood flow to and from organs.
  • Machines that combine the PET and CT images, called a PET/CT, are commonly used.

How the Test is Performed

A PET scan uses a small amount of radioactive tracer. The tracer is given through a vein (IV). The needle is most often inserted on the inside of your elbow. The tracer travels through your blood and collects in organs and tissues. This helps the radiologist see certain areas more clearly.

You will need to wait as the tracer is absorbed by your body. This takes about 1 hour.

Then, you will lie on a narrow table that slides into a large tunnel-shaped scanner. The PET detects signals from the tracer. A computer changes the signals into 3D pictures. The images are displayed on a monitor for your health care provider to read.

You must lie still during the test. Too much movement can blur images and cause errors.

How long the test takes depends on what part of the body is being scanned.

How to Prepare for the Test

You may be asked not to eat anything for 4 to 6 hours before the scan. You will be able to drink water but not other beverages including coffee. If you have diabetes, your provider will tell you not to take your diabetes medicine before the test. These medicines will interfere with the results.

Tell your provider if:

  • You are afraid of close spaces (have claustrophobia). You may be given a medicine to help you feel sleepy and less anxious.
  • You are pregnant or think you might be pregnant.
  • You have any allergies to injected dye (contrast).

Always tell your provider about the medicines you are taking. Let your provider know about the medicines you bought without a prescription. Sometimes, medicines may interfere with the test results.

How the Test will Feel

You may feel a sharp sting when the needle with the tracer is placed into your vein.

A PET scan causes no pain. The table may be hard or cold, but you can request a blanket or pillow.

An intercom in the room allows you to speak to someone at any time.

There is no recovery time, unless you were given a medicine to relax.

Why the Test is Performed

A PET scan can reveal the size, shape, position, and some function of organs.

The most common use for a PET scan is for cancer, when it may be done:

  • To see how far cancer has spread. This helps to select the best treatment approach.
  • To check how well your cancer is responding, either during treatment or after treatment is completed.

This test can also be used to:

  • Check brain function
  • Identify the source of epilepsy in the brain
  • Show areas in which there is poor blood flow to the heart
  • Determine if a mass in your lung is cancerous or harmless

Normal Results

A normal result means there were no problems seen in the size, shape, or position of an organ. There are no areas in which the tracer has abnormally collected.

What Abnormal Results Mean

Abnormal results depend on the part of the body being studied. Abnormal results may be due to:

  • Change in the size, shape, or position of an organ
  • Cancer
  • Infection
  • Problem with organ function

Risks

The amount of radiation used in a PET scan is about the same amount as used in most CT scans. These scans use short-lived tracers, so the radiation is gone from your body in about 2 to 10 hours. Having many x-rays, CT or PET scans over time may increase your risk for cancer. However, the risk from any one scan is small. You and your doctor should weigh this risk against the benefits of getting a correct diagnosis for a medical problem.

Tell your provider before having this test if you are pregnant or breastfeeding. Infants and babies developing in the womb are more sensitive to radiation because their organs are still growing.

Rarely, people may have an allergic reaction to the tracer material. Some people have pain, redness, or swelling at the injection site.

Considerations

It is possible to have false results on a PET scan. Blood sugar or insulin levels may affect the test results in people with diabetes.

Most PET scans are now performed along with a CT scan. This combination scan is called a PET/CT. This helps find the exact location of the tumor.

PET scan for breast cancer

Breast positron emission tomography; PET – breast; PET – tumor imaging – breast

A breast positron emission tomography (PET) scan is an imaging test that uses a radioactive substance (called a tracer) to look for breast cancer. This tracer can help identify areas of cancer that an MRI or CT scan may miss.

How the Test is Performed

A PET scan requires a small amount of radioactive material (tracer). This tracer is given through a vein (IV), usually on the inside of your elbow. It travels through your blood and collects in organs and tissues. The tracer helps the radiologist see certain areas or diseases more clearly.

You will need to wait nearby as your body absorbs the tracer. This usually takes about 1 hour.

Then, you will lie on a narrow table, which slides into a large tunnel-shaped scanner. The PET scanner detects signals from the tracer. A computer changes the results into 3D pictures. The images are displayed on a monitor for your doctor to read.

You must lie still during test. Too much movement can blur images and cause errors.

The test takes about 90 minutes.

Most PET scans are now performed along with a CT scan. This combination scan is called a PET/CT.

How to Prepare for the Test

You may be asked not to eat anything for 4 to 6 hours before the scan. You will be able to drink water.

Tell your health care provider if:

  • You are afraid of close spaces (have claustrophobia). You may be given a medicine to help you feel sleepy and less anxious.
  • You are pregnant or think you might be pregnant.
  • You are breastfeeding.
  • You have any allergies to injected dye (contrast).
  • You take insulin for diabetes. You will need special preparation.

Always tell your provider about the medicines you’re taking, including those bought without a prescription. Sometimes, medicines can interfere with the test results.

How the Test will Feel

You may feel a sharp sting when the needle containing the tracer is placed into your vein.

A PET scan causes no pain. The table may be hard or cold, but you can request a blanket or pillow.

An intercom in the room allows you to speak to someone at any time.

There is no recovery time, unless you were given a medicine to relax.

Why the Test is Performed

A PET scan is most often used when other tests, such as MRI scan or CT scan, DO NOT provide enough information.

A breast PET scan is used only after a woman has been diagnosed with breast cancer. It is done to see if the cancer has spread to other parts of the body, such as the lymph nodes, liver, lung, or bones.

If you have breast cancer, your doctor may order this scan:

  • Soon after your diagnosis to see if the cancer has spread
  • After treatment if there is concern that the cancer has come back
  • During treatment to see if the cancer is responding to treatment

A PET scan is not used to screen for, or diagnose, breast cancer.

Normal Results

A normal result means there are no areas outside the breast in which the radiotracer has abnormally collected. This result most likely means the breast cancer has not spread to other parts of the body.

Very small areas of breast cancer may not show up on a PET scan.

What Abnormal Results Mean

Abnormal results may mean that the breast cancer has spread.

Blood sugar or insulin level may affect the test results in people with diabetes.

Risks

The amount of radiation used in a PET scan is low. It is about the same amount of radiation as in most CT scans. Also, the radiation does not last for very long in your body.

Women who are pregnant or breastfeeding should let their doctor know before having this test. Infants and babies developing in the womb are more sensitive to the effects of radiation because their organs are still growing.

It is possible, although very unlikely, to have an allergic reaction to the radioactive substance. Some people have pain, redness, or swelling at the injection site.

Lung PET scan

Chest PET scan; Lung positron emission tomography; PET – chest; PET – lung; PET – tumor imaging; PET/CT – lung; Solitary pulmonary nodule – PET

A lung positron emission tomography ( PET ) scan is an imaging test. It uses a radioactive substance (called a tracer) to look for disease in the lungs such as lung cancer .

Unlike magnetic resonance imaging ( MRI ) and computed tomography ( CT ) scans, which reveal the structure of the lungs, a PET scan shows how well the lungs and their tissues are working.

How the Test is Performed

A PET scan requires a small amount of tracer. The tracer is given through a vein (IV), usually on the inside of your elbow. It travels through your blood and collects in organs and tissues. The tracer helps the doctor (radiologist) see certain areas or diseases more clearly.

You will need to wait nearby as the tracer is absorbed by your body. This usually takes about 1 hour.

Then, you will lie on a narrow table, which slides into a large tunnel-shaped scanner. The PET scanner detects signals from the tracer. A computer changes the results into 3-D pictures. The images are displayed on a monitor for your doctor to read.

You must lie still during test. Too much movement can blur images and cause errors.

The test takes about 90 minutes.

Most PET scans are now performed along with a CT scan. This is because the combined information from each scan provides a more complete understanding of the health problem. This combination scan is called a PET/CT.

How to Prepare for the Test

You may be asked not to eat anything for 4 to 6 hours before the scan. You will be able to drink water.

Tell your health care provider if:

  • You are afraid of tight spaces (have claustrophobia). You may be given a medicine to help you relax and feel less anxious.
  • You are pregnant or think you might be pregnant.
  • You have any allergies to injected dye (contrast).
  • You take insulin for diabetes. You will need special preparation.

Tell your provider about the medicines you are taking. These include ones bought without a prescription. Some medicines can interfere with the test results.

How the Test will Feel

You may feel a sharp sting when the needle containing the tracer is placed into your vein.

A PET scan causes no pain. The table may be hard or cold, but you can request a blanket or pillow.

An intercom in the room allows you to speak to someone at any time.

There is no recovery time, unless you were given a medicine to relax.

Why the Test is Performed

This test may be done to:

  • Help look for lung cancer, when other imaging tests do not give a clear picture
  • See if lung cancer has spread to other areas of the lungs or body, when deciding on the best treatment
  • Help determine if a growth in the lungs (seen on a CT scan) is cancerous or not
  • Determine how well cancer treatment is working

Normal Results

A normal result means the scan did not show any problems in the size, shape, or function of the lungs.

What Abnormal Results Mean

Abnormal results may be due to:

  • Lung cancer or cancer of another area of the body that has spread to the lungs
  • Infection
  • Inflammation of the lungs due to other causes

Blood sugar or insulin level may affect the test results in people with diabetes.

Risks

The amount of radiation used in a PET scan is low. It is about the same amount of radiation as in most CT scans. Also, the radiation does not last for very long in your body.

Women who are pregnant or are breastfeeding should let their doctor know before having this test. Infants and babies developing in the womb are more sensitive to the effects of radiation because their organs are still growing.

It is possible, although very unlikely, to have an allergic reaction to the radioactive substance. Some people have pain, redness, or swelling at the injection site. This soon goes away.

Brain PET scan

Brain positron emission tomography; PET scan – brain

A brain positron emission tomography (PET) scan is an imaging test of the brain. It uses a radioactive substance called a tracer to look for disease or injury in the brain.

A PET scan shows how the brain and its tissues are working. Other imaging tests, such as magnetic resonance imaging ( MRI ) and computed tomography ( CT ) scans only reveal the structure of the brain.

How the Test is Performed

A PET scan requires a small amount of radioactive material (tracer). This tracer is given through a vein (IV), usually on the inside of your elbow. Or you breathe in the radioactive material as a gas.

The tracer travels through your blood and collects in organs and tissues. The tracer helps the doctor see certain areas or diseases more clearly.

You wait nearby as the tracer is absorbed by your body. This usually takes about 1 hour.

Then, you lie on a narrow table, which slides into a large tunnel-shaped scanner. The PET scanner detects signals from the tracer. A computer changes the results into 3-D pictures. The images are displayed on a monitor for the doctor to read.

You must lie still during test so that the machine can produce clear images of your brain. You may be asked to read or name letters if your memory is being tested.

The test takes between 30 minutes and 2 hours.

How to Prepare for the Test

You may be asked not to eat anything for 4 to 6 hours before the scan. You will be able to drink water.

Tell your health care provider if:

  • You are afraid of close spaces (have claustrophobia). You may be given a medicine to help you feel sleepy and less anxious.
  • You are pregnant or think you might be pregnant.
  • You have any allergies to injected dye (contrast).
  • You have taken insulin for diabetes. You will need special preparation.

Always tell your health care provider about the medicines you are taking, including those bought without a prescription. Sometimes, medicines interfere with the test results.

How the Test will Feel

You may feel a sharp sting when the needle containing the tracer is placed into your vein.

A PET scan causes no pain. The table may be hard or cold, but you can request a blanket or pillow.

An intercom in the room allows you to speak to someone at any time.

There is no recovery time, unless you were given a medicine to relax.

Why the Test is Performed

A PET scan can show the size, shape, and function of the brain, so your doctor can make sure it is working as well as it should. It is most often used when other tests, such as MRI scan or CT scan, do not provide enough information.

This test can be used to:

  • Diagnose cancer
  • Prepare for epilepsy surgery
  • Help diagnose dementia if other tests and exams do not provide enough information
  • Tell the difference between Parkinson disease and other movement disorders

Several PET scans may be taken to determine how well you are responding to treatment for cancer or another illness.

Normal Results

There are no problems detected in the size, shape, or function of the brain. There are no areas in which the tracer has abnormally collected.

What Abnormal Results Mean

Abnormal results may be due to:

  • Alzheimer disease or dementia
  • Brain tumor
  • Epilepsy , and may identify where the seizures start in your brain
  • Movement disorders (such as Parkinson disease )

Risks

The amount of radiation used in a PET scan is low. It is about the same amount of radiation as in most CT scans. Also, the radiation does not last for long in your body.

Women who are pregnant or are breastfeeding should let their doctor know before having this test. Infants and babies developing in the womb are more sensitive to the effects of radiation because their organs are still growing.

It is possible, though very unlikely, to have an allergic reaction to the radioactive substance. Some people have pain, redness, or swelling at the injection site.

Considerations

It is possible to have false results on a PET scan. Blood sugar or insulin levels may affect the test results in people with diabetes .

PET scans may be done along with a CT scan. This combination scan is called a PET/CT.

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