Positron emission tomography (pet)

[Gregory]

Positron emission tomography (PET) is a type of radionuclide scanning. A radionuclide is a radioactive form of an element, which means it is an unstable atom that becomes more stable by releasing energy as radiation. Most radionuclides release high-energy photons as gamma rays but PET uses radionuclides that release particles called positrons.
In PET, a substance that the body uses (metabolizes), such as glucose or oxygen, is labeled with a radionuclide. The combination of this substance and the radionuclide is called a radioactive tracer. The tracer collects in specific tissues of the body. Generally, the more active the tissue (for example, the more glucose or oxygen it uses), the more tracer it collects and the more radiation it gives off.
The PET scanner contains several rings of detectors that record the radiation released. Data are recorded from many different angles. From these data, computers produce a series of 2-dimensional color images that look like slices of the body (called tomographs). The data can also be used to construct 3-dimensional images.
The images show different levels of activity in different intensities of color. Thus, PET can provide information about a tissue’s function and can identify abnormal tissues, which may be more or less active than normal tissues. However, PET does not show anatomic and structural detail of tissues and organs as well as computed tomography (CT) or magnetic resonance imaging (MRI).