Positron Emission Tomography


Positron emission tomography is a nuclear medicine functional imaging technique that is used to observe metabolic processes in the body.

Functional imaging, is a medical imaging technique of detecting or measuring changes in metabolism, blood flow, regional chemical composition, and absorption.

Nuclear medicine is a medical specialty involving the application of radioactive substances in the diagnosis and treatment of disease.

Tomography is imaging by sections or sectioning, through the use of any kind of penetrating wave.

Positron Emission Tomography | PET by CHUSherbrooke


The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide, which is introduced into the body on a biologically active molecule.

Gamma ray, denoted by the lower-case Greek letter gamma, is penetrating electromagnetic radiation of a kind arising from the radioactive decay of atomic nuclei.

The positron or antielectron is the antiparticle or the antimatter counterpart of the electron.

A radionuclide is an atom that has excess nuclear energy, making it unstable.

What is a PET scan? Positron Emission Tomography by WPOncology


Three-dimensional images of tracer concentration within the body are then constructed by computer analysis.


In modern PET-CT scanners, three dimensional imaging is often accomplished with the aid of a CT X-ray scan performed on the patient during the same session, in the same machine.

Positron emission tomography–computed tomography is a nuclear medicine technique which combines, in a single gantry, a positron emission tomography scanner and an x-ray computed tomography scanner, to acquire sequential images from both devices in the same session, which are combined into a single superposed image.


If the biologically active molecule chosen for PET is fludeoxyglucose, an analogue of glucose, the concentrations of tracer imaged will indicate tissue metabolic activity as it corresponds to the regional glucose uptake.

Glucose is a sugar with the molecular formula C6H12O6.


Use of this tracer to explore the possibility of cancer metastasis is the most common type of PET scan in standard medical care.

Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body.

Metastasis is the spread of a cancer from one organ or part of the body to another without being directly connected with it.

Metástasis is an American, Spanish-language version of the U.S. crime drama Breaking Bad.


However, although on a minority basis, many other radioactive tracers are used in PET to image the tissue concentration of other types of molecules of interest.

A radioactive tracer, or radioactive label, is a chemical compound in which one or more atoms have been replaced by a radioisotope so by virtue of its radioactive decay it can be used to explore the mechanism of chemical reactions by tracing the path that the radioisotope follows from reactants to products.


One of the disadvantages of PET scanners is their operating cost.

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