A positron emission tomography (PET) scan is a type of imaging test. It uses a radioactive substance called a tracer to look for disease in the body. A 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.
A positron emission tomography (PET) scan is a type of imaging test. It uses a radioactive substance called a tracer to look for disease in the body.
A PET scan shows how organs and tissues are working.
- This is different from 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 PET/CT, are commonly used.
How the Test is Performed
A modest amount of radioactive tracer is used during a PET scan. The tracer is administered intravenously (IV). Most frequently, the inside of your elbow is where the needle is entered. Your blood carries the tracer, which then accumulates in tissues and organs. This makes some regions easier for the radiologist to see.
As the tracer is absorbed by your body, you will need to wait. An hour is required for this.
You will then be placed on a small table that glides into a huge scanner in the shape of a tunnel. The tracer’s signals are picked up by the PET. The impulses are converted into 3D images by a computer. Your healthcare professional can view the images on a monitor.
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 no 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.
- Do 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
The most common use for a PET scan is for cancer, when it may be done:
- To see how far the 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 most often in people with symptoms of cognitive problems
- 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
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.
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 tumour.