MRI

Reference recent posting on MRI

In the world of electronic components, copper, brass, tin, gold, silver, plastics, ceramics, silicon all are commonly used, and are all non-magnetic and unaffected by the very powerful field of the MRI scanner.

Nickel is an exception.

What has been noticeable in recent years, has been the shift of component manufacturing to China.

This has given rise to cloned or counterfeit chips, chips like the ones in pacemakers. It is very unlikely that these fake components make their way into finished medical devices that have the highest manufacturing and quality standards, compared to consumer equipment like a door bell.

Another unwelcome change has been the use of steel in place of copper or brass particularly in the leads used to solder the components to the circuit board. This steel would be affected in an MRI scan.

Steel is less conductive than copper, but probably makes little difference in real life. Principally, it is done for cost-cutting.

In the UK, the old brass coinage, non-magnetic, has been replaced by brass plated steel. They look the same until you get a magnet out.

Another example of cost-cutting is in wiring and cables.

I found this out when attempting to repair a vintage electric motor and a Chinese replicate.

The old motor was easy because it soldered well with copper wire. The Chinese motor used the much cheaper aluminium wire which normally cannot be soldered and relies on mechanical connections.

You have to hope that all this is known by device manufacturers.

2 Comments

The safety of an MRI

by Gemita - 2024-07-31 08:38:26

Piglet, thank you again for your help with the translations.   

There is no doubt that when I go into an MRI environment, twice now with my current pacemaker, I am still a bit anxious.  Personally, I always feel a “heating up” of my body and this concerns me for the safety of my device and leads.  However, I know we are always told that when certain safety precautions are met, it is safe with a MRI safe device to have an MRI scan.  I am living proof of that now, surely?

For my first MRI scan I also had a Reveal Linq monitor in place too, and with two devices they were extra careful and made sure that they saved all my settings and data beforehand in case anything was lost.  

Have a look at the following excellent link from the British Cardiovascular Society for the safe scanning of patients with MRI conditional pacemakers.  It confirms that MRI can be performed if safety conditions are met:- 

damaged/abandoned or epicardial leads are not recommended; 

adequately trained personnel, monitoring and equipment are essential for the duration of the scan; 

asynchronous or inhibited programming of the device is required for the duration of the scan; 

pre and post device checks must be made; 

tachycardia therapies should be disabled.

https://www.britishcardiovascularsociety.org/resources/editorials/articles/magnetic-resonance-imaging-in-patients-with-cardiac-implantable-electronic-devices-current-recommendations

MRI up to 3 Tesla has been described as safe in patients with loop recorders implanted, for example the Reveal Linq monitor, however it is recommended to interrogate the device before the scan to save any relevant data. The MRI field is likely to generate artefact which will be stored on the device. Therefore interrogating the loop recorder and clearing its data post-scan is also recommended.

My main concern for non MRI safe devices or leads would be the potential for heating and tissue damage at the lead tip altering sensing and capture thresholds which may not be immediately detectable.   Also drainage of battery from asynchronous pacing throughout the scan could be significant in those devices nearing elective replacement indicator period (ERI).  It is recommended that patients nearing ERI have their devices changed prior to having an MRI, so lots to consider.

I too hope adequate testing is done by each manufacturer before they label their product "MRI safe when certain conditions are met"!  

Thanks Gemita

by piglet22 - 2024-07-31 09:46:28

Indeed the magnetic field in the core of the scanner is very high.

I may be wrong, but I believe they use supercooling to achieve the high currents needed.

Haemoglobin has an iron atom so I wonder if this is affected?

Oxygen is paramagnetic and exhibits magnetic qualities.

Would activation of these atoms cause your heating sensation?

I don't envy the first person to go into the early versions of these machines.

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Try to concentrate on how you’re able to be active again and feel normal, rather than on having a machine stuck in your body.