Lay Description
PET Scanning: Seeing How the Body Works
Positron Emission Tomography, or PET scanning, is a way of making images that show how the body works. In PET, a very small amount of a radioactive drug is given to a patient usually through an injection in the arm. The radioactive drug will go to certain parts of the body depending on which particular drug is used. For example, fluorine-18 labeled fluorodeoxyglucose, also called FDG, is a radioactive version of the sugar glucose. Once injected into the body, it will go to places where glucose is used for energy. For instance, the brain uses glucose as its primary source of energy, and so FDG will go to the brain, and, in particular, to those parts of the brain that are actively burning glucose for energy. If the patient is performing a certain task, such as reading a story, more FDG will go to certain regions of the brain than others.
After being injected with the radioactive drug, the patient is placed in a machine 
called a PET scanner. The PET scanner consists of thousands of small radiation detectors that measure the radiation that is being emitted by the radioactive drug within the patient. In this way, the PET scanner can make 3D images that show where the radioactive drug went in the body. In the case of FDG, these images will show those areas of the body that are actively burning glucose for energy. A PET scan shows how the body is working and not just how it looks as other forms of medical imaging, such as CAT scanning and MRI, do. Other radioactive drugs besides FDG can also be used to measure other aspects of how the body works such as the rate of blood flow in certain organs and how certain cells in the body, such as nerve cells, communicate with each other.
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PET Brain Scan |
In many cases, PET scanning is used to either find a disease or to better understand how widespread a disease is within a patient. PET scanning is commonly used for such diseases as epilepsy, Alzheimer’s disease and cancer. In epilepsy, it can be used to tell where within the brain the disease is and whether the patient is a candidate for certain methods of treating the disease. In Alzheimer’s disease, the PET scan can be used to tell if this patient truly has the disease or whether the patient’s symptoms (such as forgetfulness) are actually being caused by something else.
In cancer, PET scanning can be used to find a tumor. It can also be used to tell whether a tumor found by some other method is cancerous or whether the cancer has spread to
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PET Scan of Lung Tumor |
other parts of the body. PET scanning can do this because FDG is known to go to many types of cancerous tumors at a much higher rate than normal tissue.
PET scanning is also used in research to gain a better understanding of how our bodies work. At Wake Forest, we use PET scanning to learn about Alzheimer’s disease, dyslexia and learning disabilities, drug abuse, and cancer, as well as the biological effects of social stress and normal aging.
PET scanning is addressing many important issues in medicine as well as in basic biology. In the years to come, as we learn more about the fundamental nature of many diseases, PET scanning will be an incredibly invaluable tool as it continues to provide a unique opportunity to look inside and see how the body works.