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MRI of a joint
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An MRI of a joint is an imaging test that uses three things: magnets, radio waves and a computer that assembles the image. It uses no X-rays and no other radiation.
Where the image comes from is the beautiful part. The body is full of water, and the hydrogen in water and in other molecules contributes a single proton, a positively charged particle that spins on its own axis and behaves like a tiny magnet. With no external field, those protons point every which way. When the machine turns on its magnetic field, they line up with it, some parallel and some antiparallel. Each proton is a tiny compass needle that the magnet lines up. Because a few more end up parallel than antiparallel, that small excess leaves a net magnetic vector, a sum pointing in one direction, and that is where the signal used to build the image comes from.
And MRI shows soft tissue clearly, so it is one of the tests used to look at joints such as the knee or the shoulder.
In brief
MRI is an imaging test that uses magnets, radio waves and a computer, and it does not use radiation.
Hydrogen protons, tiny spinning magnets, line up either parallel or antiparallel to the field, and the signal comes from the net vector of the small parallel excess.
Each proton is a tiny compass needle that the magnet lines up.
It shows soft tissue clearly and is used to look at joints such as the knee or the shoulder.
Sources (2)
- MedlinePlus, U.S. National Library of MedicineMRI Scans, MedlinePlusPublished
- National Center for Biotechnology Information, StatPearls PublishingMagnetic Resonance Imaging Physics, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
Updated