Positron emission tomography (PET) is an examination method used in nuclear medicine. It is used in the diagnosis of tumors and to detect metastases in the body. PET can also provide information on certain diseases of the brain and heart.
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Positron emission tomography (PET) is a nuclear medical examination.
It uses low-level radioactive substances. With the help of PET, metabolic processes and blood circulation in the tissue can be better recognized. These radioactive substances (radionuclides) emit positrons. These are positively charged components of atoms.
The radionuclides are first coupled to certain substances such as sugar. They are then injected into the patient's vein as radiotracers . Via the bloodstream, they reach the various tissues and organs of the body, each of which has a different sugar requirement.
Organs with a high energy turnover, such as the brain or heart, require particularly high levels of sugar. It therefore accumulates more in these tissues. The radioactive radiation emitted from there can be measured.
The strength of the radiation can be visualized using PET. It then shows the distribution of the radioactively labeled sugar molecules. This allows conclusions to be drawn about the sugar metabolism: for example, whether it is impaired or even not functioning at all.
Based on this, doctors can also use positron emission tomography to
recognize.
PET makes metabolic processes in the body visible and can therefore also be used for tumor diagnostics © samunella | AdobeStock
The radionuclides used in nuclear medicine only have a short half-life. This is the time it takes for a radioactive substance to lose half of its radiation potential.
FDG (F18 deoxyglucose) is frequently used in cancer diagnostics. This is a glucose molecule labeled with radioactive fluorine whose half-life is less than two hours. With such short half-lives, the risk of endangering the patient and the environment is low.
Nevertheless, positron emission tomography must not be carried out on pregnant or breastfeeding women.
Compared to surrounding healthy tissue, malignant tumors also exhibit, among other things
circulation. Therefore, the radionuclide injected before the positron emission tomography examination also accumulates more strongly in the tumor cells. This enables doctors to detect cancerous tumors and also determine their size.
PET is therefore a helpful diagnostic procedure in the search for primary tumors, as well as lymph node and distant metastases.
The differentiation between benign and malignant findings in the
is also possible with positron emission tomography. The detection of blood flow and metabolism also makes it possible to differentiate between living (vital) and already destroyed tumor tissue. Positron emission tomography can therefore also be used to monitor the success of treatment after
and chemotherapy and, if necessary, change the treatment strategy in good time.
However, the spatial resolution of PET technology is limited. Therefore, altered structures are only noticeable if they are at least around five to eight millimeters in size.
Furthermore, not every increased metabolic activity is a tumor. Inflammatory processes also show up similarly in the PET image.
Targeted therapy is always based on an accurate diagnosis. Positron emission tomography alone is not sufficient for diagnosis. Other diagnostic procedures are therefore always used.
Positron emission tomography is not universally applicable in the search for tumors and metastases. So far, primary tumors in the head and neck area, such as
can be detected.
The positron emission tomography examination device looks similar to a computer tomograph(CT).
The patient lies on an examination table, which is slowly moved through a detector ring, the so-called PET scanner. The scanner detects the incoming radiation.
With the help of the scanners, computers can, similar to computer tomography
images. The examination of the entire body takes between 45 and 60 minutes.
The positron emission tomograph looks similar to a CT scanner, which can be seen here © Gorodenkoff | AdobeStock
Patients should generally have an empty stomach before the PET scan. Drinks are allowed.
The patient takes the drinking solution with the radiotracers around one hour before the examination. It then has enough time to disperse in the body.
To ensure that the radionuclide does not remain in the body for long, the patient should drink a lot after the examination. The radioactive substances are then quickly excreted via the kidneys and bladder.
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