Antimatter might sound like something from science fiction or the latest Dan Brown novel, but this exotic material is now routinely produced in laboratories around the world, and has even found its way into medical imaging that is used for brain enhancement. In the form of a positron emission tomography (PET) scan, antimatter is used to take pictures that show not only what the inside of the body looks like, but how it functions.
How a Positron Emission Tomography Scan Works
The matter of which our bodies are made – and all the matter we can see around us – is formed from a small number of tiny building blocks called fundamental particles. Antimatter is identical to matter except that certain physical properties of each particle are reversed. For example, the electron is a type of particle that carries a negative electrical charge, while its antiparticle, the positron, carries a positive charge. When a particle encounters its antiparticle, the pair are both destroyed with a sudden release of energy.
- To obtain a PET scan, a substance that emits positrons (a “radiotracer”) is injected into the patient’s bloodstream. The most common radiotracer is a radioactive form of glucose called FDG, which is taken up by the body’s cells.
- The patient then lies inside the PET scanning machine, which contains detectors that measure the pulses of energy generated when positrons from the FDG are destroyed together with electrons in the patient’s tissues.
- A powerful computer analyses the data from the detectors, to produce a three-dimensional image of the area of interest.
Cancer Diagnosis and Treatment Monitoring with PET Scans
Cancer cells grow faster than normal cells and so take up larger amounts of glucose. As a consequence, cancers accumulate large quantities of FDG during a PET scan and are visible as bright regions on the resulting image.
At present, PET scanning is mainly used to diagnose and monitor the treatment of lymphoma and lung cancer, to look for cancers that have spread to other parts of the body (metastases), and to show whether a cancer that was previously cured has returned. PET scans may also be useful for diagnosing cancer of the head and neck, oesophagus or brain.
PET Scanning for Early Signs of Dementia in Alzheimer’s Disease
During a PET brain scan, it is thought that the amounts of FDG taken up by the different parts of the brain are related to the level of activity within each part. Scans of people with Alzheimer’s disease show characteristic patterns of activity in the brain, and so PET scanning may help to detect early signs of dementia before they become physically apparent.
Other Uses of the PET Scan Machine
Apart from the applications described here, PET scanning is still most commonly used for scientific research. Other possible medical uses include:
- identifying where seizures originate in the brain of people with epilepsy
- diagnosing other brain lesions
- looking for defects in the structure and function of the heart and blood vessels.
PET – Nuclear Medicine Using Antimatter
The PET scanner was invented in 2000, so PET is still a relatively new medical imaging technique. It is currently very expensive and is available in only a few hospitals; patients referred for a PET scan will usually have to travel some distance to the nearest facility. A radioactive tracer is injected into the bloodstream, but the type of radiation used in a PET scan disappears very rapidly from the body. The amount of radiation to which the patient is exposed is similar to that experienced in a CT scan.