MRI Machines 101: Understanding The Differences

August 25, 2020 – 6 min read

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image of a woman lying on an MRI platform

Magnetic Resonance Imaging (MRI) is a complex imaging machine that utilizes a very strong magnet. As a patient lies in the magnetic field, a radio wave is used to send signals to the body and receive them back. The returning signals are converted into images by a computer attached to the scanner. MRI scanners are available in different magnetic field strengths, measured in teslas or “T” and varying sizes, including open and wide-bore. In today’s post, we discuss the differences between these machines and what you can expect when you make an appointment for an MRI scan at a Touchstone Imaging center near you.

It is important to note that no one single MRI machine is “better” than any other. There are a variety of MRI machine options to meet the various MRI needs. While one patient may be better suited with a stand-up open MRI, another may be better served with a 1.5T wide-bore. The differences we discuss today should help you better understand the procedure you are going to have and help clarify why your ordering physician or MRI technologist suggested one over the other — or, in some cases, it doesn’t matter which machine is used.

Before we jump right into the different machines available at the various Touchstone Imaging centers across the United States, let’s first discuss a few of the features that make up an MRI machine and where they can vary. Magnetic strength – the image quality of an MRI depends on signal and field strength and ranges from 0.5 to 3.0 tesla (T). Magnet strengths affect the radio waves that respond and create the image. It may seem like the higher the tesla, the better the machine, however, for those with implanted devices, a lower tesla offers a less likelihood of displacing objects.
In addition to varying magnet strengths, bore size also affects the functioning and use of the MRI machine. The bore of an MRI machine is the center or the opening of the machine. The area around the bore is where the magnet is housed. Traditional MRI scanners had 60 cm bore, which limited who could use them due to the size of the patient or claustrophobia. Over the last decade, larger bore machines with a 70 cm bore make scanners more comfortable but require a higher strength magnetic field.

MRI Machines Used at Touchstone Imaging

3T Wide Bore MRI

A 3T machine has a greater signal strength than other MRI machines, in fact, it is the greatest strength an MRI machine can have. 3T MRI scanners create extremely clear and vivid images that can be completed quicker. 3T MRIs are ideal for imaging small bones, breast tissue, musculoskeletal structures, the brain and spine, and vascular flow. While the 3T MRI is great for these fine-detail things, it does have a higher likelihood of artifact — capturing images that are not there — caused by movement, due to the speed and intensity of the imaging.

1.5T Wide Bore MRI

As we discussed above, the teslas refer to magnetic strength, so a 1.5T has half that of a 3T MRI machine. 1.5 T MRIs are great for visualizing the brain or abdomen, where artifact is more likely to occur on a 3T. For those who have implanted devices — joints, pacemakers, stents, etc. — or other metal in their body, including bullets or shrapnel, the 1.5 is a much safer option. Some people assume, based on the numbers, that the 1.5T is inferior to the 3T, but both are great machines, offering diagnostic images that can make all the difference in treatment and outcome.

Highfield Open MRI

A Highfield MRI, like its name implies, is a higher-powered magnetic field in a somewhat more open MRI than the traditional machines. This makes it ideal for patients who are claustrophobic or cannot be accommodated by closed-bore MRI machines but require a higher tesla than what is offered by a truly open MRI. It is considered an open MRI because instead of being a long tube that is closed on one end, it is open on both ends — more reminiscent of a CT scanner — and is flared on the sides to increase the tesla power. The bore exists on all four sides but is much more open. As you can imagine, this does not allow for as high of a magnetic field as that of wide-bore traditional machines, and can only get up to 1.2T. The images produced are still great quality and detailed, allowing your physician to make an accurate diagnosis.

Open MRI

An open MRI machine offers the best option for those who are truly claustrophobic and for larger patients who cannot be accommodated by other bores. Options include upright or lying. The machine has two sides that sandwich the patient in the middle rather than closing them in — more similar to an x-ray machine. Because it does not have four sides, the tesla rating is much lower, usually 0.5 to 0.6T. While open MRI machines are more advanced, they may not offer the same detail as closed scanners and can take more time to produce images. The benefits of an open MRI is more open space, which means it can accommodate more body types. An open MRI machine is great for both patient and physician, however, some conditions may require closed MRI to be used, in which case a Highfield MRI may be better suited.

When deciding which MRI is right for you, your MRI technologist or ordering physician may discuss your options in terms of your current conditions and the pros and cons of each machine. If you suffer from claustrophobia, an open MRI may be your only choice, but for the vast majority of people, the reduced time a closed MRI takes is enough to quiet some anxieties. View some of our other posts for more information about your upcoming MRI and what to expect.

FAQ About MRI 
The Different Kinds of MRI and What to Expect
Claustrophobia and MRI
Ways Your MRI Technologist Helps Make the Procedure More Comfortable
Tips to Make Your MRI More Comfortable

All MRI machines are useful in capturing images of internal organs and structures, which can help make an accurate diagnosis and lead to effective treatment. The MRI technologists at Touchstone Imaging are experts at helping decide which is best for your condition and capturing the best quality images possible. Additionally, if your physician recommends a closed or Highfield MRI over an open one, our technologists can help quell your fears and ease your anxiety. We have decades worth of experience, and all of our staff are friendly and accommodating to your unique needs. For more information or to schedule your MRI, find a Touchstone Imaging center near you and contact us today!