PET - positron emission tomography
What is Positron Emission Tomography?
Positron emission tomography (PET or PET scan) the diagnostic tests available physiological images, the detection of positrons by an example of the activity of cell and tissue images can be generated. Positrons emitted from a radioactive substance administered to the patient is small particles. PET, ie, (emissions) radioactive detection of qualitative and quantitative understanding of the organization preparing the way for a nuclear medicine scan. Images obtained with this technique are used to investigate a variety of diseases.
What is the procedure?
Most commonly used PET to detect cancer, pre-staging of the cancer and to examine the effects of cancer treatment on cancer tissue. While other imaging methods such as X-rays, CT and MRI only shows pictures of the "appearance" of a cancer, PET can show if the tumor is active or inactive - that distinguish scar tissue from active tumor tissue. Such knowledge may be crucial for the further treatment of a patient. The survey can also be used to find the source of a cancer that has spread, distinguishing between benign and malignant tumors. Especially useful PET has proven to be lung cancer, malignant melanoma, esophageal cancer, cancer of the head and neck region, thyroid cancer, breast cancer, cancer of the colon and rectum, ovary cancer, lymphoma.
The picture taken of the entire body. Often combined PET and CT images in order to achieve a more precise localization of the changes that had to be demonstrated. PET images of the brain can be used to assess patients with memory disorders of unknown cause, suspected of having a brain tumor who have epilepsy (seizures) that do not improve with medication and who may be candidates for surgery.
PET images of the heart can be used to determine blood flow to the heart muscle and can help in the assessment of coronary artery disease (angina pectoris and myocardial infarction). PET images of the heart can also be used to identify the areas of the heart that have reduced function, is still alive or if it is just scar tissue from previous heart attack. PET may help to distinguish non-functional cardiac muscle from muscles that may benefit from a treatment such. angioplasty or coronary by-pass, treatments that can improve blood flow and cardiac function. PET is particularly useful for this purpose in overweight, because fat tissue to a small extent the radiation.
What happens during the PET examination?
Before starting the test system and the body's general cyclotron radioactive material substance, most commonly glucose (blood sugar), but sometimes water or ammonia, "attachment" and called the drug is injected into the patient, the drug's specific body sites and detected by the PET scanner.
Different colors or degrees of light intensity of a PET image representing different amounts of tissue or organ function. For example, healthy tissue using glucose as energy source and some of the radiolabeled glucose will appear on the PET images. Cancerous tissue, which uses more glucose than normal tissue, will absorb more of the radioactive substance and appear as brighter than normal tissue on the PET images.
How do I prepare for the examination?
PET is usually performed, ie in patients who are not admitted to hospital. Your doctor will give you detailed instructions on how to prepare for the examination. Wear comfortable, not too tight clothes. You should not have eaten the last four hours before the test, but you are encouraged to drink water. You need to keep you nice and warm in the hours preceding the survey, for "frost in the body" may interfere with the interpretation. Your doctor will advise you about the use of any regular medication prior to the study.
What does the "PET machine" out?
PET scanner has a hole in the middle and looks like a large donut. Inside the machine there are many rings that records sent (emitting) of positrons from the radioactive substance is injected into your body, and makes it possible to produce an image of the body. While lying on the examination table, the table is moved into the hole in the machine. The images displayed on a screen of a computer in the control room where the examination takes place.
How is the survey?
A nurse or techniques will take you into the examination room. You lie down on the examination table and get a shot of the radioactive substance is inserted directly into the bloodstream (intravenously). It will then take about. 30-60 minutes where the radioactive material flows around the body and is taken up into the tissue to be examined. During this period you will be asked to relax, the lighting is dim, you screened for chatting and you'd better be at rest - so avoid that the localization of the radioactive substance affected.
So start recording image. It takes an additional 25 minutes. Usually there are no restrictions after the investigation is completed, but you are encouraged to drink plenty to flush out the radioactive substance from your body.
Will I notice anything during the exam?
The injection of the radioactive substance is like a conventional syringe prick. You lie and relax. During the shooting, you have to be at rest. Some might feel a little tendency to claustrophobia, and for some it can be difficult to remain completely still so long. You will not feel any discomfort due to radioactivity in the body. The radioactive substance will quickly disappear after investigation and involves no health risk for you.
Who interprets the results?
Usually it is a radiologist with specialized training in interpreting PET images considering the pictures and make a report to the doctor who referred you. Usually it takes only a few days before results are available.
What are the advantages and disadvantages of the survey?
Because PET allows study of body function, it can help physicians detect changes in the biochemical processes that suggest disease before changes in anatomy, for example. CT or MRI.
Because radioactivity is very short, the radiation exposure is very low. The radiation is so small that it does not affect the normal processes of the body.
The radioactive substance may expose the fetus to radiation if you are pregnant or may get into breast milk if you are breastfeeding. The risk to the fetus or child must be weighed against the potential benefit of PET study.
What limits the PET?
PET can give false results if your chemical balance is abnormal. This applies particularly diabetics or patients who have eaten the last hours before the test, because it can affect your blood sugar and insulin levels in the body. Since the radioactive substance decays quickly and seems only a short time, it must be produced in a laboratory near the PET machine. It is important that you arrive on time to the study.
PET performed by a physician who specializes in nuclear medicine, and who has experience with PET. In July 2005, installed the first full PET machine. In December 2005, also installed a machine at the hospital.
The utility of PET images increases when they are part of a larger diagnostic evaluation. In particular, comparisons with other imaging methods such as CT and MRI are useful. As already mentioned, a combination study of PET and CT to provide more accurate information about the location of any findings.
There is still some uncertainty about the accuracy of PET, ie the risk of making false positive and negative findings.
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