PET scan

Positron Emission Tomography – Computed Tomography (PET/CT)

What is Positron Emission Tomography – Computed Tomography (PET/CT) Scanning?

Sample image obtained using a combination of PET and CT imaging technology.
Positron emission tomography, also called PET imaging or a PET scan, is a type of nuclear medicine imaging.
Nuclear medicine is a branch of medical imaging that uses small amounts of radioactive material to diagnose or treat a variety of diseases, including many types of cancers, heart disease and certain other abnormalities within the body.
Nuclear medicine or radionuclide imaging procedures are noninvasive and usually painless medical tests that help physicians diagnose medical conditions. These imaging scans use radioactive materials called radiopharmaceuticals or radiotracers.
Depending on the type of nuclear medicine exam you are undergoing, the radiotracer is either injected into a vein, swallowed or inhaled as a gas and eventually accumulates in the organ or area of your body being examined, where it gives off energy in the form of gamma rays. This energy is detected by a device called a gamma camera, a (positron emission tomography) PET scanner and/or probe. These devices work together with a computer to measure the amount of radiotracer absorbed by your body and to produce special pictures offering details on both the structure and function of organs and tissues.
A PET scan measures important body functions, such as blood flow, oxygen use, and sugar (glucose) metabolism, to help doctors evaluate how well organs and tissues are functioning.

What are some common uses of the procedure?
PET and PET/CT scans are performed to:

• detect cancer
  
• determine whether a cancer has spread in the body
  
• assess the effectiveness of a treatment plan, such as cancer therapy
  
• determine if a cancer has returned after treatment
  
• determine blood flow to the heart muscle
  
• determine the effects of a heart attack, or myocardial infarction, on areas of the heart
  
• identify areas of the heart muscle that would benefit from a procedure such as angioplasty or coronary artery bypass surgery (in combination with a myocardial perfusion scan).
  
• evaluate brain abnormalities, such as tumors, memory disorders and seizures and other central nervous system disorders
  
• to map normal human brain and heart function

How should I prepare for a PET and PET/CT scan?
You may be asked to wear a gown during the exam or you may be allowed to wear your own clothing.
You should inform your physician and the technologist performing your exam of any medications you are taking, including vitamins and herbal supplements. You should also inform them if you have any allergies and about recent illnesses or other medical conditions.
You will receive specific instructions based on the type of PET scan you are undergoing. Diabetic patients will receive special instructions to prepare for this exam.

Metal objects including jewelry, eyeglasses, dentures and hairpins may affect the CT images and should be left at home or removed prior to your exam. You may also be asked to remove hearing aids and removable dental work.
Generally, you will be asked not to eat or drink anything for several hours before a whole body PET/CT scan since eating may alter the distribution of the PET tracer in your body and can lead to a suboptimal scan. This could require the scan to be repeated on another day, so following instructions regarding eating are very important. You should inform your physician of any medications you are taking and if you have any allergies, especially to contrast materials, iodine, or seafood.
You will be asked and checked for any conditions that you may have that may increase the risk of using intravenous contrast material.

How is the procedure performed?
Nuclear medicine imaging is usually performed on an outpatient basis, but is often performed on hospitalized patients as well.
You will be positioned on an examination table. If necessary, a nurse or technologist will insert an intravenous (IV) line into a vein in your hand or arm.
Depending on the type of nuclear medicine exam you are undergoing, the dose of radiotracer is then injected intravenously, swallowed or inhaled as a gas.
It will take approximately 90 minutes for the radiotracer to travel through your body and to be absorbed by the organ or tissue being studied. You will be asked to rest quietly, avoiding movement and talking.
You may be asked to drink some contrast material that will localize in the intestines and help the radiologist interpreting the study.
You will then be moved into the PET scanner and the imaging will begin. You will need to remain still during imaging. The PET scan takes 45 minutes.

What will I experience during and after the procedure?
Most nuclear medicine procedures are painless and are rarely associated with significant discomfort or side effects.
If the radiotracer is given intravenously, you will feel a slight pin prick when the needle is inserted into your vein for the intravenous line. When the radioactive material is injected into your arm, you may feel a cold sensation moving up your arm, but there are generally no other side effects.
It is important that you remain still while the images are being recorded. Though nuclear imaging itself causes no pain, there may be some discomfort from having to remain still or to stay in one particular position during imaging.