The PET (from the English Positron Emission Tomography) o Positron Emission Tomography is a nuclear medicine exam that allows you to study the whole human body with a "high resolution and provides information on the metabolism of internal organs and tissues. It is used in the oncology sector but also in the neurological and cardiology sector. PET is distinguished from other nuclear medicine tests, such as scintigraphy and SPET (or tomoscintigraphy) by the type of radioactive tracer.
PET can use a substance normally present in the body (for example, glucose) to bind the administered radioactive substance (such as Fluorine 18 in the case of glucose). Once in circulation, the radioactive tracer emits particular particles, called positrons, which are recorded by a special scanner placed outside the body (tomograph or detection system).
The PET machine is very similar to a CT machine because it consists of a ring within which the bed that houses the person is positioned. The image returned by the tomograph allows us to evaluate how these tracers are distributed within an organ or a specific biological tissue. All intensively active cells consume glucose and, as a result, glucose will accumulate more in these areas of the body. In areas where cellular activity is very high, the radioactive tracer will emit a more intense and clearly visible signal. For example, in oncology, cancer cells are very active and need more energy than healthy ones. cases the glucose will accumulate in the areas with metastases and the radioactive tracer will make them visible and well identified.
The applications of PET in oncology concern almost all types of tumors since it is possible to use the most suitable radiopharmaceuticals for each type: brain tumors, head and neck, lung, breast, gastrointestinal, genitourinary, of bones, muscles and soft tissues, lymphomas and myelomas, melanoma, endocrine and neuroendocrine neoplasms. The PET exam, due to its characteristics, is used to diagnose tumors, to understand the best place to take a biopsy, to understand at what stage the tumor is but also to verify the effectiveness of treatments in course.
To exploit even better the characteristics of the PET examination, equipment called PET-TAC has been developed that can record images related to the functioning of an organ or tissue (PET image) simultaneously with information on their shape and composition (morphological images) normally given by the CT scan. This type of examination allows to locate even better the organ or tissue where the radiopharmaceutical has accumulated.THE TEST
During a PET exam, a small amount of radioactive drug is administered intravenously, which does not generate any risk for family members living together. In fact, immediately after the end of the exam, you can go home, following the instructions of the health workers regarding the precautions to be taken towards children and pregnant women.
Before starting the exam, you are asked to remove metal objects that could interfere with the exam and create artifacts in the images. During the examination the patient lies down and the tomograph collects the data (the tomograph does not emit radiation).
Everyone can undergo a PET scan, if necessary and on the recommendation of the treating doctor, except pregnant women to avoid any risk to the fetus. If you are breastfeeding it is necessary to report this to your doctor to receive instructions on the period in which breastfeeding must be interrupted in order to prevent the substance circulating in the woman's body from passing through the milk to the baby.
To undergo the PET scan it is often necessary to fast in the six hours preceding the examination. You can freely drink water and beverages but they must not be sweetened so as not to change the result of the investigation. Often, before performing the PET scan, the blood glucose level is measured. It is always important to strictly follow the instructions given by the doctor when booking the exam.Bibliography
Italian Association of Nuclear Medicine (AIMN)
World Health Organization (WHO). Nuclear Medicine (NM) exams in childrenIn-depth link
International Atomic Energy Agency (IAEA). Radiation Protection in nuclear medicine
Italian Association of Medical and Health Physics (AIFM). Nuclear Medicine and the Medical Physicist
Italian Association for Cancer Research (AIRC). PET (Positron Emission Tomography)