How Antimatter is Used in Medicine



When many people think of antimatter, they think of science fiction movies like Star Trek, where the Starship Enterprise is powered by antimatter engines.
Lately in JC Physics we have been discussing nuclear physics, and in particular the phenomenon of positron decay. A positron is a particle that has the same mass as an electron, but positive charge instead of negative charge. When a positron and an electron touch each other, they annihilate each other, releasing energy in the form of gamma radiation.

There is a real world medical application of this called Positron Emission Tomography. The word tomography means getting an image by sectioning using penetrating waves. Suppose there is a tumor in the brain and there is a lot of blood internally near the tumor. The doctors need to locate exactly where the tumor is inside the brain – exact 3 dimensional coordinates. So they inject a radioactive isotope into the blood stream and this radioactive isotope produces positrons. The positron very quickly hits an electron and produces not just one but two gamma rays. The gamma rays move in opposite directions and are detected by a big spherical detector, enabling the doctors to map out the flow of blood throughout the brain. High emission represents high blood concentration, which shows you the location of the tumor.

Pretty wild stuff wouldn’t you say? Inside your brain, matter and antimatter are annihilating each other and you are actually a source of gamma radiation. The good news is you don’t need very much gamma radiation to get a good image. So the exposure you get is not really dangerous. And this is a very effective medical tool that is used all over the world now.

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