PET scan, also called PET-CT or positron emission computed tomography, is an exam normally indicated to investigate cancer, evaluate the possibility of metastasis and monitor the development of the tumor and response to treatment.
The PET scan exam is quick and safe, as the substance, which is marked by a radioactive substance, emits radiation in small concentrations, and is easily eliminated after the exam through urine.
The PET scan is an exam available in health plans and the SUS that is only performed for the investigation, diagnosis and monitoring of lung cancer, lymphomas, colon cancer, rectal cancer and immunoproliferative diseases, such as multiple myeloma, which is a disease in which blood cells begin to proliferate and accumulate in the bone marrow.
What is it for
PET scan is a diagnostic test that serves to evaluate the metabolic activity of cells through the consumption of radioactive markers, the most common being glucose, known as “FDG”, very useful in the diagnosis and staging of various types of cancer and also in evaluating response to treatment.
When is indicated
PET scan examination may be indicated in the following situations:
- Cancer investigation and diagnosis;
- Detection of neurological problems, such as epilepsy and dementia;
- Assessment of the extent of cancer in different organs (search for metastases);
- Monitoring the evolution of cancer;
- Monitoring response to therapy.
The PET scan may also be able to determine, in some cases, the diagnosis and sometimes define the prognosis, that is, the chances of a favorable outcome or not.
How is the preparation
It is important to follow the doctor’s instructions on preparing for the exam to avoid interfering with the exam results. Therefore, it is recommended that the day before the exam, the person eats lightly and does not practice physical activity. It is also important to inform about the use of medications, as some need to be suspended for 24 hours.
It is also recommended that the person fast for around 6 hours before taking the exam.
How is done
The PET-scan exam is quick and considered safe, being carried out by administering a tracer directly into the vein, which is normally glucose labeled with a radioactive substance. Then, you must wait 1 hour for the tracer to be absorbed by the body and the test can be carried out.
The PET scan takes a reading of the body, capturing the radiation emitted and forming images. In the investigation of tumor processes, for example, the consumption of glucose by cells is very high, as glucose is the source of energy necessary for cell differentiation. Thus, the image formed will have denser points where there is greater glucose consumption and, consequently, greater radiation emission, which can characterize the tumor.
After the exam, it is important that the person drinks plenty of water so that the tracer can be eliminated more easily. Additionally, there may be mild allergy symptoms, such as redness, at the site where the tracer was injected.
The test has few contraindications and can even be carried out in people who have diabetes or kidney problems. Pregnant or breastfeeding women cannot undergo this diagnostic test, as a radioactive substance is used that can affect the baby.
Bibliography
- SANTOS, Marcos. et al. ONCOLOGICAL GUIDELINES. 2nd ed. Brasília: 2018. 573-589.
- Robilotta CC. Positron emission tomography: a new modality in Brazilian nuclear medicine. Rev. Panama. Public health. Vol.20. 134-142, 2006
- BRAZILIAN SOCIETY OF NUCLEAR MEDICINE. PET/CT FDG-18F. 2015. Available at: <https://sbmn.org.br/wp-content/uploads/2015/11/PET-CT-FDG.pdf>. Accessed on May 25, 2020
