Learn more. Positron emission tomography PET is a type of nuclear medicine procedure that measures metabolic activity of the cells of body tissues. PET is actually a combination of nuclear medicine and biochemical analysis.
Used mostly in patients with brain or heart conditions and cancer, PET helps to visualize the biochemical changes taking place in the body, such as the metabolism the process by which cells change food into energy after food is digested and absorbed into the blood of the heart muscle. PET differs from other nuclear medicine examinations in that PET detects metabolism within body tissues, whereas other types of nuclear medicine examinations detect the amount of a radioactive substance collected in body tissue in a certain location to examine the tissue's function.
Since PET is a type of nuclear medicine procedure, this means that a tiny amount of a radioactive substance, called a radiopharmaceutical radionuclide or radioactive tracer , is used during the procedure to assist in the examination of the tissue under study. Specifically, PET studies evaluate the metabolism of a particular organ or tissue, so that information about the physiology functionality and anatomy structure of the organ or tissue is evaluated, as well as its biochemical properties.
Thus, PET may detect biochemical changes in an organ or tissue that can identify the onset of a disease process before anatomical changes related to the disease can be seen with other imaging processes such as computed tomography CT or magnetic resonance imaging MRI. PET is most often used by oncologists doctors specializing in cancer treatment , neurologists and neurosurgeons doctors specializing in treatment and surgery of the brain and nervous system , and cardiologists doctors specializing in the treatment of the heart.
However, as advances in PET technologies continue, this procedure is beginning to be used more widely in other areas. PET may also be used in conjunction with other diagnostic tests, such as computed tomography CT or magnetic resonance imaging MRI to provide more definitive information about malignant cancerous tumors and other lesions.
Originally, PET procedures were performed in dedicated PET centers, because the equipment to make the radiopharmaceuticals, including a cyclotron and a radiochemistry lab, had to be available, in addition to the PET scanner.
Now, the radiopharmaceuticals are produced in many areas and are sent to PET centers, so that only the scanner is required to perform a PET scan. Further increasing the availability of PET imaging is a technology called gamma camera systems devices used to scan patients who have been injected with small amounts of radionuclides and currently in use with other nuclear medicine procedures.
These systems have been adapted for use in PET scan procedures. The gamma camera system can complete a scan more quickly, and at less cost, than a traditional PET scan.
Discuss any recent illnesses, medical conditions, medications you are taking and allergies — especially to contrast material. Your doctor will likely tell you not to eat anything and to drink only water for several hours before your scan. Leave jewelry at home and wear loose, comfortable clothing. You may wear a gown during the exam. Nuclear medicine uses small amounts of radioactive material called radiotracers. Doctors use nuclear medicine to diagnose, evaluate, and treat various diseases.
These include cancer, heart disease, gastrointestinal, endocrine, or neurological disorders, and other conditions. Nuclear medicine exams pinpoint molecular activity. This gives them the potential to find disease in its earliest stages. They can also show whether you are responding to treatment. Nuclear medicine is noninvasive. Except for intravenous injections, it is usually painless. These tests use radioactive materials called radiopharmaceuticals or radiotracers to help diagnose and assess medical conditions.
Radiotracers are molecules linked to, or "labeled" with, a small amount of radioactive material. They accumulate in tumors or regions of inflammation. They can also bind to specific proteins in the body. The most common radiotracer is F fluorodeoxyglucose FDG , a molecule similar to glucose. Cancer cells are more metabolically active and may absorb glucose at a higher rate. This higher rate can be seen on PET scans. This allows your doctor to detect disease before it may be seen on other imaging tests.
FDG is just one of many radiotracers in use or in development. You will usually receive the radiotracer in an injection. Or you may swallow it or inhale it as a gas, depending on the exam. It accumulates in the area under examination.
A special camera detects gamma ray emissions from the radiotracer. The camera and a computer produce pictures and supply molecular information.
Many imaging centers combine nuclear medicine images with computed tomography CT or magnetic resonance imaging MRI to produce special views. Doctors call this image fusion or co-registration. Image fusion allows the doctor to connect and interpret information from two different exams on one image. This leads to more precise information and a more exact diagnosis.
It is not currently available everywhere. A PET scan measures important body functions, such as metabolism. It helps doctors evaluate how well organs and tissues are functioning. CT imaging uses special x-ray equipment, and in some cases a contrast material , to produce multiple images of the inside of the body. A radiologist views and interprets these images on a computer monitor. CT imaging provides excellent anatomic information. These combined scans help pinpoint abnormal metabolic activity and may provide more accurate diagnoses than the two scans performed separately.
Women should always tell their doctor and technologist if they are pregnant or breastfeeding. See the Safety in X-ray, Interventional Radiology and Nuclear Medicine Procedures page for more information about pregnancy and breastfeeding related to nuclear medicine imaging. Tell the doctor and your exam technologist about any medications you are taking, including vitamins and herbal supplements. List any allergies, recent illnesses, and other medical conditions.
You will receive specific instructions based on the type of your PET scan. Diabetic patients will receive special instructions to prepare for this exam. The scanner takes about 30 minutes to produce detailed images of metabolic activity in your tissues and organs.
A positron emission tomography PET scan is an imaging test that can help reveal the metabolic or biochemical function of your tissues and organs. The PET scan uses a radioactive drug tracer to show both normal and abnormal metabolic activity.
A PET scan can often detect the abnormal metabolism of the tracer in diseases before the disease shows up on other imaging tests, such as computerized tomography CT and magnetic resonance imaging MRI. The tracer is most often injected into a vein within your hand or arm. The tracer will then collect into areas of your body that have higher levels of metabolic or biochemical activity, which often pinpoints the location of the disease.
A PET scan is an effective way to help identify a variety of conditions, including cancer, heart disease and brain disorders. Your doctor can use this information to help diagnose, monitor or treat your condition.
Cancer cells show up as bright spots on PET scans because they have a higher metabolic rate than do normal cells. PET scans may be useful in:. PET scans must be interpreted carefully because noncancerous conditions can look like cancer, and some cancers do not appear on PET scans. This PET image shows an area of reduced blood flow from one of the arteries that feeds the heart. This information may help doctors decide whether to suggest bypass surgery or angioplasty to restore that blood flow.
PET scans can reveal areas of decreased blood flow in the heart. This information can help you and your doctor decide, for example, whether you might benefit from a procedure to open clogged heart arteries angioplasty or coronary artery bypass surgery.
A PET scan can compare a normal brain left with one affected by Alzheimer's disease right. The loss of red color with an increase in yellow, blue and green colors shows areas of decreased metabolic activity in the brain due to Alzheimer's disease. PET scans can be used to evaluate certain brain disorders, such as tumors, Alzheimer's disease and seizures. PET: physics, instrumentation, and scanners. An Introduction. Is there any pain involved, and how long does the test take?
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Skip to content. This post aims to explain what positron emission tomography PET is and how it works. Synthesis of radiotracers: The radiotracers used in a PET scan are synthesised in a cyclotron.
Protons accelerated by the cyclotron knock and replace neutrons from the isotope of oxygen, forming radioactive F Since the half-life of F is only minutes, it has to be incorporated into glucose to form FDG very quickly.
The end product, FDG is identical to glucose, except that the second OH group has been replaced by the radioactive F made in the cyclotron: Skeletal formula of FDG bottom and glucose top. Decay and distribution of FDG: When FDG taken up into a cell, it is phosphorylated into FDG-phosphate [5] , and this molecule cannot be broken down further, so is therefore trapped in the cell.
Annihilation and Detection: A positron is the anti-matter match to an electron — it has identical properties but an opposite charge. Image credit: astronomy. Diagram showing LOR and coincidences. Credit: depts. PET: physics, instrumentation, and scanners [8] med-ed. Leave a Reply Cancel reply Your email address will not be published.
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