Lights, batteries and strong magnetic fields

LEDBE
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notrefined

Enlightened
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so as I'm standing inside the 500 gauss line in front of a 3 tesla MRI scanner this evening, I started to wonder what might be the most appropriate light for that setting, and what variables actually matter. I take this as not being *too* absurd, because I already had a light with me in my MRI compatible laryngoscope handle. Now, I imagine that anything microprocessor controlled might be at least questionable, though we certainly have microprocessor controlled (I assume) monitors and ventilators in the MRI suite, which are also certified MRI compatible. Big chunks of stainless steel also clearly a bad idea, but perhaps brass would be better than something less dense because it has the mass to weigh down the small amounts of ferrous metal that might be present in a light. Other questions that came to mind:
Is any one battery chemistry likely to have less ferrous component than another?
Are there inherent problems with LEDs and magnetic fields, or is an LED just as suitable as an incan bulb?
 
Interesting question. I thought stainless steel was non-ferromagnetic because of the presence of nickel?

I think the battery casing will have the most steel in the cell.
 
nickel is also magnetic, aluminum is a good bet. titanium wouldn't be horrible, as far as battery chemistry goes i have no idea, but a direct drive type of light, not requiring a driver like you said seems about perfect
 
um, the LED and IC drivers are not the problem to my knowledge. The battery and casing is. The heat sink for the LED may be.

My older daughter is starting medical school shortly, but was/is working as an EMT in ambulances and as an MRI Tech at a University to teach the doctors/PhDs how to use MRI. In general for the readers of this thread, flashlights of any kind are banned from the MRI area even the little button cell versions. Only lights that are MR Conditional to 3T are allowed close, and the associated MR batteries are sold separately. The last price I saw was $209 per MR-qualified battery - with certs. Don't ask about the price of the light.... The serious MRI work is performed in separate buildings with warning signs on the outside of the building.

Normal consumer batteries have a ferrous-based case enclosing the chemical paste - not allowed anywhere near the room. eg: some flashaholics use magnets to attach the charging leads to the anode/cathode of their batteries.
 
further off-topic addendum: as a moldyoldy, I have had the privilege of over an hour in that narrow MRI tunnel for a total of 3 MRI scans listening to the electro-magnets pound away around me. Ironically, much of my engineering training at the U in Fields theory was running thru my head at the time. How many gauss at what rate, etc. etc. I was amazed at the variety of pulse modes and perceived power in each mode. ...and I fell asleep towards the end.... :) .

I also was the subject of a CAT scan to ensure that there was nothing metallic inside my body (military veteran). The tech was worried because she was about to hit me with the full 3 Tesla of her machine. The finer the resolution the tech is trying to achieve, the greater the power to the field. ie: a 3 Tesla MRI machine gives higher resolution or "better" results than a more usual 1.5 Tesla MRI machine.

so in a weak attempt to get back on topic of flashlights and batteries, I have the basis to imagine what 3 Tesla would do to a flashaholic flashlight in that room - for a very brief while it would fly....!

It is amazing what medical technology is available to keep all of us around a few years more........
 
Last edited:
C-Beam said:
Interesting question. I thought stainless steel was non-ferromagnetic because of the presence of nickel?

I think the battery casing will have the most steel in the cell.
Click to expand...

It's the chromium content that makes it "stainless", not the nickel.

There are several classes of stainless steels. Some of them are magnetic, some of them not so much. Austenitic stainless steels don't tend to be very magnetic, where ferritic and martensitic stainless steels usually are.
 
There are some flashlights that change modes based on magnets.

For instance, the Nitecore SR3 and the Jetbeam RRT.

I have found these lights do not function properly if a mangetic spacer is used at the head of the cell.

So a few LED lights are sensitive to magnetic fields.
 
An LED light with a driver in it probably has an inductor in it. The behavior of the inductor will change if it is saturated (magnetic field exceeds a certain amount). So the circuit could be damaged or just misbehave.

Greg
 
interesting, I had assumed that our MRI compatible handle had standard alkaline batteries in it like all of our other handles...didn't think to check, but I will the next time I'm down there.
 
Simple test: if a magnet sticks to it, I wouldn't chance it. Aluminum or even plastic would be your best bet for the body

A cheapo with no regulation would more likely suit the bill, since it would mean less transistors to blow and less blow to the wallet. I can't predict anything about an LED... an LED is also a semi-conductor, but to blow it the current would have to be induced to a metallic part in the circuit, and since most of it made of copper, it shouldn't be a big problem. I would fear that the battery contacts (springs) could be conductive, though, but you could tet that with a magnet.

For the batteries I would also rely on the magnet test, as the insides are usually made of very thin wafers rolled in a spiral and possibly not very ferro-magnetic.... the bigger foreseeable problem is induced current that could blow up the batteries

Magnetic fields respond to the exact same law as light and any source of radiation: inverse square law. Distance is your friend if you want to be subjected to the least amount (except for light, where regular walls and eyelids tend to work just fine) You could also get an insulation box from the magnetic field (often called a zero-chamber), but I don't know how much of a difference it would make, since you would want a good opening facing more or less towards or into the machine...

And then if you really want to go ahead with this, why not put it in a plastic container for the first test or two... just in case...
 
I'm surprised no company has come up with a fiber-optic system with the lightbox in another room and a few drops of fiber near the MRI unit.
 
I wouldn't bring anything that's not known to be made of MR compatible materials into the room.

Even testing it with a regular magnet isn't 100%, as you don't know how the magnet's strength at a certain distance compares to the MR magnet's strength at another distance. I think at the research lab where I used to work, there was a specific magnet for testing that had the numbers worked out already. I don't know if there is something similar in the clinical MR suites.

Vinniec5 said:
I'm surprised no company has come up with a fiber-optic system with the lightbox in another room and a few drops of fiber near the MRI unit.
Click to expand...

Probably not necessary as there are MR compatible lights and other equipment. In the MR suite where I worked, there were only limited access ports for which you can pipe your own tubing or fiber.
 
Simple test: if a magnet sticks to it, I wouldn't chance it. Aluminum or even plastic would be your best bet for the body

A cheapo with no regulation would likely be preferable, since it would mean less transistors to blow and less blow to the wallet. I can't predict anything about an LED... an LED is a semi-conductor, but to blow it the current would have to be induced to a metallic part in the circuit.

For the batteries I would also rely on the magnet test, as the insides are usually made of very thin wafers rolled in a spiral and possibly not very ferro-magnetic.... at least hopefully...

Magnetic fields respond to the exact same law as light and any source of radiation: inverse square law. Distance is your friend if you want to be subjected to the least amount (except for light, where walls tend to work just fine) You could also get an insulation box from the magnetic field (often called a zero-chamber), but I don't know how much of a difference it would make, since you would want an opening facing more or less towards or into the machine...

And then if you really want to go ahead with this, why not put it in a plastic container for the first test or two... just in case;)
 
from a "stronger" perspective, my daughter works in an MRI research facility. Clinical work is normally 1.5T, although some scans are done on a 3T machine. However the smallest MRI machine that they have is 3Tesla. As far as I know, any equipment certifications stop at 3T conditional. They also have a 7T, a couple 9.4T and are installing a 16T machine. 16 Tesla? My mind does not cope with a magnetic field that strong, much less any portable equipment "near" it. I suspect that all portable anything is or will be banned from the area when the 16T is running. Flashaholics need not bother asking about any handcarried flashlight!
 
Are you sure they're testing MRI's? and not developing a S.D.I. Rail gun??:whistle: 16T with that strong a field it might suck the metal flake outta your paint job:D. Hope some day the 007 bullet deflecting Rolex may become a reality:thumbsup:
 
16 Tesla is pretty much the peak of "normal" MRI research. FWIW, There is a video on YouTube of a live frog being levitated by a 16Tesla field. The frog is kinda flopping around in mid-air. If the field can levitate a frog - evidently there are some iron pigments in the frog's skin - think of what a 16T field would do to any metallic object, magnetic or not! Just about any kind of flashlight would become a projectile if close - no definition of "close" either!
 
Titanium seems to do good in an MRI. I have 6 screws and 2 rods in my back and had 3 MRI scans of that area in a 3 week period. My nack problem is the nect vertebra up.

But no issue with the metal.
 
We have a research 9T, and though I've never had any reason to go over there, we have reports of people getting pre-syncopal (dizzy, about to pass out) from moving or turning too fast near the machine. At least one person claims this is because the field is strong enough to affect blood flow, though i haven't researched the topic.
 
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