All About Gradient Coils in Magnetic Resonance Imaging (MRI)

by | Sep 9, 2021 | MRI

Reading Time: 2 minutes

Every MRI scanner has gradient coils inside, but little is actually known about them. These gradients are essentially loops of thin conductive sheets or wire on a cylindrical shell. Within an MRI scanner, they’re just within the bore. Understanding this is crucial when calling for MRI coil repairs.


Understanding Gradient Coils

When a current passes through gradient coils, a second magnetic field gets made. When there is a gradient field, there’s a slight distortion with the key magnetic field. The pattern is usually rather predictable, which leads the protons’ resonance frequency to vary. Essentially, gradients are meant to allow the MR signal to be encoded spatially. Gradients are vital for a variety of physiologic techniques: perfusion imaging, diffusion, and MR angiography.

Spatial coding generally happens thanks to a frequency getting changed. This happens when a gradient is applied, which causes protons to have a frequency variation. This occurs along the gradient’s direction, as a function of position. When the gradient gets played in the midst of slice selection then signal readout, then it’s possible to pick a slice that’s perpendicular to the direction of the gradient.

In the past, gradient coils were made of individual wires wrapped in fiberglass cylindrical formers. They also had a lot of epoxy resin coated on them as well. This method is still used by a number of laboratory instruments alongside high-field human scanners. 

Through the years, technology has advanced, and modern changes have happened in the medical field. Today, superconducting scanners that are widely manufactured will make use of distributed windings in a “fingerprint” pattern. It had large copper sheets or several thin metallic strips that are etched into complicated patterns in the cylinder.

The general standard with MR systems is to have a trio of gradient coil sets. These gradients are x-, y-, and z-. Every coil set is powered by an independent power amplifier, leading to a gradient field with a z-component that varies. The x-, y-, and z- directions vary linearly as well.  X- and y- (transverse) gradients typically have Golay, a saddle coil design. On the other hand, the basis for Z-gradient designs are Maxwell: circular coils. 


Reasons for an MRI Repair

When the coils of your MRI need repair, that means a failure has occurred. Here are three of the most common reasons why an MRI repair is necessary:

  • Failure due to impact – This includes instances when the coil isn’t handled well or gets dropped somehow.
  • Frequent use – Like with anything else, when something is used often, it’s prone to breaking down over time.
  • Improper use – A good example of this is using coils in conjunction with each other that aren’t a good fit in any sense.



Having an understanding of your MRI system will come in handy when calling for repair. One major part of the system are gradient coils, which play a key role in the entire system. They are responsible for the spatial coding, which helps the scanning process along. Most, if not all,MR systems have three gradient coil sets.

Are you in need of mechanical MRI coil repair? DirectMed Parts has you covered. Rest assured that DirectMed Parts has professionally trained, top-of-the-line professionals on the team. We specialize in CT and MRI parts and coils, and our team is well aware of the importance of delivering accurate, high-quality parts in a timely manner.


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