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'Why Is an MRI so Loud?' And Other Questions from the Bore

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Working for a company in the medical imaging equipment industry, I look at this equipment a little differently. Whenever a friend or family member has a procedure done, I’m asking, “Which machine?" "Which manufacturer?"  "Didn’t you ask?” 

Of course, these questions are probably far different than those running through the mind of the average MRI patient. So, when I had an MRI of my own done (it was on a GE Excite 1.5T, FYI), I tried to put myself in their metaphorical shoes and think about what they would ask. The longer I laid there, the more questions came to mind, namely, these three:

• Why is an MRI machine so loud? (I had to wear ear plugs)

• Why is an MRI machine so big?

• What do the numbers on the machine mean? 

I decided to go to our in-house MRI experts here at Block Imaging- Steve Rentz and Randy Bolenbaugh- for answers.

 

Why Is an MRI Machine so Loud?

An MRI has four magnets inside it- a large principle magnet and three smaller magnets. The smaller magnets (gradients) are inside a large metal coil called a gradient coil. As electrical current is applied to the MRI to create an image, the coil expands and contracts rapidly (you could even think of it as vibrating) causing the loud noise you hear as you pass through the bore. 

 

Why Is an MRI Machine so Big?

Inside_of_MRIBefore I had this MRI done, I had the rare opportunity to see inside an MRI (see photo). It was quite large and, truth be told, it seemed to have a lot of empty space. Unlike, say, a CT scanner, MRIs have very few moving pieces. So why are they so huge? The answer came in two parts:

Field strength- In order to create a magnetic field large enough to operate an MRI, you need a BIG magnet.

Constant cooling- In order to keep a magnet stable, it must be kept cool constantly. Currently, we use liquid helium to do this. The amount required is large, ergo, a large amount of space is required to contain it.

 

What do the numbers on an MRI machine mean?

The answer to this question also came in two parts.

Table Position- One display you're likely to see on an MRI machine indicates the position of the table. In my case, there was a particular number that needed to be on the display to indicate that my knee was in the proper position for the best scan possible.

Magnetic Field Strength- The other number I saw fluctuated between 1.0 and 1.5. This number indicated the strength of the magnetic field. The reading varied between 1.0T and 1.5T depending on which degree of field strength was needed for each specific image. 

There was a time- before working here at Block, before I ever had an MRI scan- when I wouldn't have given a second thought to the inner workings of medical equipment. Now that I'm drawn to them by both my work and my experience, I’m glad I had in-house experts to turn to for answers. If you have questions about MRI equipment, service, parts, or anything else- feel free to contact us for more information.

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