THE ELEMENT
How PET scans utilise antimatter In 1982, Paul Dirac discovered new equations to describe how particles such as electrons behave when travelling close to the speed of light (shown below). However, upon completion, he found that his equation always had two possible solutions, much as the √4 = ∓2. For his equation, one answer described the electron, however one described something with the same mass and spin as the electron but with an opposite charge: an antielectron, also known as a positron. This is a type of antimatter. Dirac's equation proved true not only for just electrons, but also for other kinds of particles: quarks have antiquarks and because quarks make up protons, antiprotons also exist. Similarly, antiprotons and antielectrons can make up antiatoms and so on.
Positrons can be used for medical purposes in positron emission tomography (PET) scans which construct images to check for things such as checking brain function, metastasis, the body's response to a cancer treatment or examining blood flow. PET works by using a scanning machine to detect photons emitted by a radioisotope, an atom with excess nuclear energy, in the organ being examined. These radioisotope are
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made by a particle accelerator called a cyclotron through this process: 1. A negatively charged hydrogen ion is injected into the vaccum chamber of the cyclotron where two D shaped plates are enclosed between the poles of a strong electromagnet 2. An alternating positive and negative voltage is sent through the D shaped plates which attracts and repels the ion in a circular path. Each time the ion passed the gap between the D shaped plates, it accelerates as it gains energy
3. On the outside of the D shaped plates is extraction foil. When the ion reaches the outside and hits this foil, it is stripped of its electrons, leaving a positively charged proton 4. This proton travels down a beamline towards a target containing atoms. When the proton collides with the nucleus of an atom in the target, a nuclear reaction changes the atoms structure which creates the radioisotope The radioisotope is then added to a molecule that is easily absorbed by the body such as a sugar, hormone or
