What is positron emission tomography (PET Scan)?
A positron emission tomography (PET scan) scan is an imaging test that helps reveal how your tissues and organs are working. The PET scan uses a radioactive drug (tracer) to show this activity. This scan can sometimes find disease before it shows up on other imaging tests.
The tracer can be injected, swallowed, or inhaled depending on the organ or tissue being studied. The marker accumulates in areas of your body that have high levels of chemical activity, often corresponding to diseased areas. On a pet scan, these areas appear as bright spots.
A positron emission tomography scan can be used to reveal or diagnose a number of conditions, including many cancers, heart disease, and brain disorders. PET images are often combined with CT or MRI scans to create unique views.
Why is it done?
A positron emission tomography scan is an effective way to check chemical reactions in parts of your body. It can help diagnose a wide variety of conditions, including many cancers, heart disease, and brain disorders. Images from a PET scan may provide different information than other types of scans, such as computed tomography (CT) or magnetic resonance imaging (MRI).
Positron emission tomography (PET) or computed tomography (PET) scan allows your doctor to better diagnose the disease and evaluate your condition.
Cancer: Cancer cells appear as bright spots on positron emission scans because they have a higher metabolic rate than normal cells. Positron emission tomography scans can help:
- Detecting cancer
- Reveal if your cancer has spread
- Check if cancer treatment is working
- Detect cancer recurrence
Positron emission scans need to be understood carefully because non-cancerous conditions are like cancer and some cancers do not show up on positron emission scans. Positron emission tomography scans show several types of solid tumors, including:
- Head and neck
- Heart disease
PET scans reveal areas of reduced blood flow to the heart. This information can help you and your doctor, for example, if you may benefit from a procedure to open a blocked coronary artery (angioplasty) or coronary artery bypass surgery.
Uses of PET scan
- Diagnose cancer
- Determine if cancer has spread throughout the body
- Evaluate the effectiveness of the treatment
- Find out if cancer has come back after treatment
- Assess the prognosis
- Assess the metabolism and viability of tissues
- To determine the effects of myocardial infarction in areas of the heart
- Identify areas of the heart muscle that may benefit from angioplasty or coronary artery bypass surgery (including myocardial perfusion scan)
- Evaluate brain abnormalities such as tumors, memory impairment, seizures, and other central nervous system disorders
- Map the normal functioning of the human heart and brain
The procedure of PET scan
Nuclear medicine imaging is performed on patients and hospitalized patients.
- You lie on the exam table. If needed, a nurse or technician can insert an intravenous (IV) catheter into your arm or arm.
- Positron emission tomography scans only use radiotracer injections.
- Radioradiotherapy usually takes 30 to 60 minutes to travel through the body and is absorbed by the area examined. You are asked to rest quietly and not move or speak.
- You may be asked to drink some contraindications that are localized to the intestines and will help the radiologist who will describe the test.
You will be transferred to a PET / CT scanner to begin imaging. It should still be there during the imaging. A CT scan is done first, followed by a PET scan. Sometimes a second CT scan followed by a PET scan with IV contrast. For more information on how a CT scan is done, see CT Scan. The CT scan takes less than two minutes. The pet scan takes 20-30 minutes. The total scan time is usually 30 minutes.
Depending on the area being tested, additional tests with other tracers or medications may be used. This can extend the processing time to three hours. For example, if you are being tested for heart disease, you may have a positron emission tomography before and after exercise or before and after receiving IV medications, which can increase blood flow to the heart.
When the test is complete, the technician may ask you to wait until the images are verified if more images are needed. Sometimes more images are obtained to clarify or better visualize certain areas or structures. The need for more images does not mean that there was a problem with the test or that something unusual was found. This should not worry you.
If you insert an intravenous (IV) line for the procedure, it will be removed if you don’t schedule another procedure that requires an IV on the same day.
During and after the PET scan
With the exception of intravenous injections, most nuclear medicine procedures are painless. They are rarely associated with significant discomfort or side effects. When the radiotracer is given intravenously, you feel a slight sting when a needle is inserted into the vein for the IV.
You may feel a cold sensation when moving your hand up when injecting the radiotracer. In general, there are no other side effects. Positron emission tomography scans only use radiotracer injections. With some procedures, a catheter can be inserted into the bladder. This can cause temporary discomfort.
It is important to stay calm during the test. Nuclear imaging is also painless. However, staying stable or in a certain position while taking pictures can cause discomfort. If you are afraid of confined spaces, you may feel anxious during the test. If your doctor doesn’t tell you, you can resume your normal activities after the test. The technician, nurse, or doctor will give you the specific instructions you need before you leave.
A small amount of radiotracer in your body loses its radioactivity over time through the natural process of radioactive decay. During the first hours or days after the test, it can pass out of your body through urine or stool. Drink lots of water to help flush radioactive material from your body.
Results of PET scan
Pictures from a positron emission tomography scan display bright spots where the radioactive tracer collected. These spots reveal higher levels of chemical activity and details about how your tissues and organs are functioning. A doctor specially trained to interpret scan images (radiologist) will report the findings to your doctor.
The radiologist may also compare your positron emission tomography images with images from other tests you’ve undergone recently, such as computerized tomography (CT) or magnetic resonance imaging (MRI). Or the pictures may be combined to provide more detail about your condition.