6 ms·
Fun fact: if you’ve ever had a PET scan, you’ve had antimatter generated and annihilated within your own body, and you most likely survived the process.
by jl6 3y ago
Fun fact: if you’ve ever had a PET scan, you’ve had antimatter generated and annihilated within your own body, and you most likely survived the process.
- nonameiguess 3y agoNo likely here. Anyone reading this definitely survived the process.
- halfmatthalfcat 3y agoGhosts browsing HN are offended
- tgv 3y agoHow so?
- eigenket 3y agoThe letters PET stand for Positron Emission Tomography. It works by you ingesting a material that emits positrons. Positrons are antimatter electrons, they annihilate with electrons in your body and produce EM radiation which is detected by the scanner machine.
- gpderetta 3y agoMore specifically, the material emits high energy photons, that almost immediately "decay" into positron/electron pairs that travel at almost exactly opposite directions. Then detectors at opposite ends of the machine detect the electron and the positron, match the event pairs and can then reconstruct the line of travel and the emission depth (from the detection timestamp delta). IANAP, but did a bit of work on tomographic image reconstruction. edit: never mind, I got that wrong (it has been a while...): the material does emit a positron that decays into opposite photon pairs.
- eigenket 3y agoI am a physicist and you have it pretty close to correct, except reversed. The atom emits a positron (and in the process turns one of its protons into a neutron), the positron annihilates with an electron and this produces opposite photon pairs which are detected.
- heavyset_go 3y agoWhere does the electron come from, the body? Or is it generated in pairs with the positron or something?
- deleted 3y ago[deleted]
- eigenket 3y agoYeah, the positron hits an ambient electron from somewhere in the environment, in a PET scan this is usually inside the body.
- bonzini 3y ago... which is why it's called ionizing radiation, removing an electron (or adding it in the case of beta decay) turns neutral atoms into ions.
- eigenket 3y agoIn general yes. In this specific case not entirely, because once the radiating nucleus has undergone positron emission it has turned one of its protons into a neutron, which means it now needs one less electron in order to form a neutral atom. The "spare" electron can wander off and replace (eventually, on average) the electron that gets annihilated by the positron.
- platz 3y agoHow does a photon survive going through the body to make it to the detector? Seems like there is a lot of stuff in the way.
- short_sells_poo 3y agoThere's an old saying: "the dose makes the poison" :)
- labster 3y agoFun fact: bananas also produce antimatter, and generate antimatter in your body once consumed.