Positron Emission Tomography | Application

Positron emission tomography (PET) is a computed tomography technique that uses positron detection. It is also called positron emission tomography, abbreviated as PET. A radiopharmaceutical, typically a glucose analog such as Fluorodeoxyglucose (FDG) that has been labeled with a positron-emitting isotope, is introduced into the body. This substance then accumulates in cells with high metabolic activity, such as cancer cells. PET scanners observe bodily functions by detecting the pair of gamma rays produced when positrons, emitted from a radiopharmaceutical, annihilate with electrons in the body's tissues. While CT primarily provides detailed anatomical images, PET provides functional information by visualizing metabolic processes. A key advantage of PET is its ability to scan the entire body in a single session to assess widespread metabolic activity, which is particularly useful for detecting cancer metastasis. Since it can observe the metabolic level of the central nervous system, it is also used to diagnose epilepsy and Alzheimer's disease.

In recent years, it has come to be used for cancer screening by detecting elevated levels of glucose metabolism in tumor tissues. Since it can screen the entire body, it is also used to detect cancer metastasis and unexpected cancers. The method used for cancer screening is called FDG-PET, in which a radioactive substance with a structure similar to that of sugar, which is used by cancer cells for metabolism, is administered into the body and its movement is observed. It is characterized by the fact that it is easy to detect active cancers and leads to effective treatment. The radiation exposure from a PET scan is carefully managed to be as low as reasonably achievable. When combined with CT in a PET/CT scanner, the total dose is a sum of both imaging modalities, providing comprehensive anatomical and functional information.

PET scanners consist of a ring of detectors. Each detector assembly typically includes a scintillator crystal that converts incoming gamma rays into flashes of light. These light flashes are then captured by a photodetector, such as a Photomultiplier Tube (PMT) or an Avalanche Photodiode (APD), which converts the light into an electrical signal. This signal is then amplified and processed by a computer to reconstruct a three-dimensional image.

There are various ways to convert the light emitted from the scintillator into electronic energy, such as using an Image Intensifier (I.I.), a Photomultiplier Tube (PMT), or an Avalanche Photodiode (APD) and Microchannel Plate (MCP). These detectors require high voltages of 100 to 5,000 V.

Matsusada Precision offers a variety of high-voltage power supplies for PET scanners.

How PET-CT apparatus works