The MRI magnet is the core component of a magnetic resonance imaging scan machine. Its job is to create a very strong, uniform, and extremely stable magnetic field required for diagnostic quality imaging. Without this superconductive electromagnet, MR imaging is not possible.
MRI stands for magnetic resonance imaging. The magnetic part comes from the powerful superconductive electromagnet. For a closed MRI scanner, the magnet typically produces a uniform magnetic field in the 1 Tesla to 3 Tesla range, with the most common MRI magnet strength being 1.5 Tesla.
“How MRI Magnets Work (and Why They’re So Powerful)” from the MRIPETCTSOURCE YouTube Channel
This magnetic field, which is hundreds to tens of thousands of times stronger than the earth’s magnetic field, causes the hydrogen atoms in the body to align in a predictable way along the main axis of the magnetic field. When radio waves, tuned to the specific resonance frequency of the targeted atoms, are applied and then turned off, the atoms emit signals that create detailed images.
The resolution of the MRI images depends heavily on how stable, strong and uniform the magnetic field is. Even tiny changes in the magnetic field can distort images and cause artifacts.
Engineers make the MRI magnet from coils of superconducting wire, usually using a niobium titanium alloy embedded in copper. The actual superconductive wire is only about 1 millimeter in diameter and the main MRI coils require between 5,000 and 8,000 windings, which comes out to about 20 kilometers of wire per MRI magnet. The coils carry very large electrical currents, often in the 700 to 750 amp range, and because a liquid helium bath supercools them, they experience no electrical resistance. This allows MRI magnets to stay powered on 24 hours, but this is only possible if cryogen technicians keep the niobium titanium coils and the MRI cryostat extremely cold, near 4 kelvin.
The main MRI coils are multiple separate coils that together comprise the Main MRI magnetic field. On the outside we have the largest of the coils windings, the maxwell coils, also known as the primary windings. They generate the main uniform magnetic field required for imaging. These coils are carefully shaped and positioned to create a highly uniform magnetic field within the imaging volume.
Additionally, secondary windings are added to fine tune the field and correct and large scale distortions caused by the magnet geometry or the clinical environment
On the outside of the primary and secondary coil windings, shielding windings surround the main coil assembly to generate opposing magnetic fields that limit how far the magnetic field extends outside the MRI scanner. The shielding windings reduces fringe magnetic fields, improves patient safety, and helps reduce disturbance to nearby electronics. This is 18 to 24 small, adjustable magnetic windings that help compensate for minor imperfections and real time environmental influences.
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Read more on Larry’s author page.
MRI laser alignment landmark assembly with class 2 laser
CT scan ring artifact explained. CT scan machine pictured left, CT ring artifact example pictured right.
2025 MedicalImagingSource.com – Images available for licensed use. Learn more.
The information provided by MRIPETCTSOURCE (“we,” “us,” or “our”) on https://www.medicalimagingsource.com (the “Site”) is for general informational purposes only. All information on the Site is provided in good faith, however we make no representation or warranty of any kind, express or implied, regarding the accuracy, adequacy, validity, reliability, availability, or completeness of any information on the Site. UNDER NO CIRCUMSTANCE SHALL WE HAVE ANY LIABILITY TO YOU FOR ANY LOSS OR DAMAGE OF ANY KIND INCURRED AS A RESULT OF THE USE OF THE SITE OR RELIANCE ON ANY INFORMATION PROVIDED ON THE SITE. YOUR USE OF THE SITE AND YOUR RELIANCE ON ANY INFORMATION ON THE SITE IS SOLELY AT YOUR OWN RISK.
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