Effects of magnetic fields on material (Magnetic resonance)

[mahblah]

TL;DR Summary

Can Magnetic Resonance alter Gore-Tex?

Hi,
I was wondering if a Magnetic Resonance (+contrast) can in some way modify the structure of artificial chordae used in heart surgery. My first answer would be "No". There ain't any medical article about that. Also (as far as i know) I don't think magnetic field can break chemical bond, so it should not be able to alter chemical structure nor mechanical properties of ePTFE (Gore-Tex).
At the same time Magnetic Resonance involve all the atoms of a material, so maybe some collective change can be possible (and my answer would again be "No").

All these question arises form my need to perform a MRI (its not a life threatening need) and the artificial chordae inside my heart that keeps me healty. If anyone has any kind of hint or ideas about that i would be more than happy to know his point of view.

 

[Dale]

It is good that you are thinking of such safety issues. Many people go to a MRI exam without good information about their implanted device or its associated risks.

The first step is to determine the manufacturer of your implant and any model number or device designation. The manufacturer is required by law to test the safety of their device and designate it as “MR Safe”, “MR Conditional”, or “MR Unsafe” based on that direct and documented experimental evidence.

“MR Safe” means the exam can proceed without any worries. “MR Unsafe” means the exam is prohibited and your physician needs to formulate a new plan.

“MR Conditional” means that the manufacturer has developed a set of conditions that are required for safe scanning of a patient with their device implanted. The imaging facility needs to operate the scanner in a manner such that they stay within those conditions. You can speak with the technologist performing the exam about the measures that they will take to operate within the required conditions. They are trained for this and generally will be glad to tell you all that they do to make your specific exam safe and effective.

The MRI safety website ( https://www.mrisafety.com/ ) contains a searchable list of implants and their conditions. Searching for “ePTFE” returns a list of only 8 devices, all of which are listed as MR safe

https://www.mrisafety.com/TMDL_list.php?qs=ePTFE

Please confirm that your device is one of those 8 and read the relevant details.

 

[mahblah]

Artificial chordae are marked as safe. But usually safe means: "external magnetic field does not exert forces on them".
I am instead intrested in the possibility that magnetic field can alter the material.

ePTFE is a diamagnetic material (teflon, which is almost te same, has Magnetic susceptibility of -10.28E-6). So I think it should almost have no problem of "modification" or "alteration"... but I don't know enough about that.

 

[Dale]

But usually safe means: "external magnetic field does not exert forces on them".

MR Safe means much more than that. When I have done device testing for MR we have a suite of about 9 test categories with sub-tests within each category. The forces are just the first category.

Anyway, if your device is designated as MR Safe by the manufacturer, then no special concern is needed.

 

[f95toli]

Also, generally speaking the moderate magnetic fields used for MRI can not "modify" the structure of a material in any way.
At most it can magnetise a ferromagnetic material (for example iron), but even that does not really mean that the material "changes structure "; all you are doing is aligning the magnetic domains (which already exist) with the magnetic field (then the material is not "magnetic" the domains are randomized).

You can try this for yourself using a rare-earth magnet, close the magnet (af few mm) the field strength will be similar to what is used in an MRI machine.

 

[berkeman]

You can try this for yourself using a rare-earth magnet, close the magnet (af few mm) the field strength will be similar to what is used in an MRI machine.

Oh great. So you are saying "You can try this at home!"

 

[f95toli]

Why not ? The question was if a ~1Tesla magnetic field can change the properties of ePTFE
Rubbing a rare-earth magnet on say a Gore-tex jacket should convince you that the answer is no (although it might magnetise metallic buttons if they are made of iron......

 

[berkeman]

I thought you were suggesting that the OP could wave the magnet over their, you know...

 

[mahblah]

Thanks for all the reply!