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I work in a hospital. I was just curious, what is a safe distance to have a watch from an MRI machine before the risk of getting magnetized?

Whist I'm on the subject; whats a safe distance for a human? Our office has an MRI machine on the floor directly above and it does affect out cell phone signals.

:think:
 

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I guess we need to know how many Tesla the machine is.

http://www.watch-pop.com/omega_2/watch-18554.html

The "fringe field" is the term used to describe the magnetic field outside of the magnet and is also called the stray field. The rate at which the field strength diminishes or becomes weaker as you travel away from the MRI machine, depends on a few of factors and can and will vary from manufacturer to manufacturer: field strength of the magnet and whether or not the magnet is shielded either actively or passively. Most MRI machines for patient use are in the range of .065 Tesla (.065T) to 3.0 Tesla (3.0T). The majority of them are 1.5T. The 5 gauss line (the distance at which the static magnetic field does not affect pacemakers and other medically implanted devices) on a General Electric Signa 1.5T actively magnetically shielded MRI scanner, for example, is about 4 meters. 1 Tesla = 10,000 gauss so, at 4 meters, you are at about .0005T. This should be a safe distance for a watch, especially if it is said to be anti-magnetic. For a watch to be rated as anti-magnetic, it has to be able to be subjected to 4,800 a/m (60 gauss or .006T) and not lose or gain more than 30 seconds/day. The Ball Engineer Hydrocarbon watch, for example, can withstand magnetic fields of 12,000 a/m (somewhere around .015T). I may be wrong, but, I think that is one of the most "anti-magnetic" watches available. In a nutshell, don't even go anywhere near your 21 Tesla NMR machine if you want your automatic watch to live. Even at 1.5T, I keep my automatics safely off my wrist and on my desk when I approach my MRI machines. I've lost a few many years ago and have learned my lesson.
 

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I'm an MRI technologist and my recommendation is that you not take a mechanical or analog quartz watch into an MRI scan room. My work watches are all G-shocks and none have experienced any problems from working around the scanner. On many occasions I have had to stop employees (mostly physicians) from wearing their analog watches into the scan room. Most brush my warnings aside and tell me their watch is "anti-magnetic". If that happens, I refuse them entry into the room until we can discuss what "anti-magnetic" really means.
 
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Never thought I'd say this on this Omega forum, but why not buy a Rolex Milgauss - designed for EXACTLY this kind of use.
 

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Never thought I'd say this on this Omega forum, but why not buy a Rolex Milgauss - designed for EXACTLY this kind of use.
Except it's not.

The anti-magnetic rating of the Milgauss is significantly less than the field of a 1.5T magnet let along a 3T.

1T ~ 10,000 gauss. And the magnetic resistance of a Rolex Milgauss? 1,000 gauss. So really unsuitable even for our weakest MR magnets :)

I'm a radiographer and work about 15m from our 3T magnet room and I don't find my mechanical watches affected at all.
 

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My work watches are all G-shocks and none have experienced any problems from working around the scanner.
I'm working for air products and fill MRI's with Helium

are you sure that a g-shock is resistant to 3 tesla machines i have the DW-5600E and a G-7800B

 

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I'm an MRI technologist and my recommendation is that you not take a mechanical or analog quartz watch into an MRI scan room. My work watches are all G-shocks and none have experienced any problems from working around the scanner. On many occasions I have had to stop employees (mostly physicians) from wearing their analog watches into the scan room. Most brush my warnings aside and tell me their watch is "anti-magnetic". If that happens, I refuse them entry into the room until we can discuss what "anti-magnetic" really means.
Funny, true story.

I once had to accompany a patient in an MRI suite and was by his side during his procedure. I was wearing an old analogue quartz Swiss Army officer watch at the time. The procedure felt like it was taking forever, but I kept glancing at my watch and saw that hardly any time had passed. Well, later that afternoon, a colleague commented about how I had been gone for more than an hour and a half, and looking at my watch saw that only around 25 minutes had elapsed according to the watch.

So, even though people may be aware of the effects on magnetizing mechanical movements, it's also possible to affect the movement of non-mechanical watches as well, and I think pretty unreliably.

Can't comment on the digital/ G-shock option.
 
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Totally off topic here, but can anyone who is an MRI tech perhaps PM me as I have a question. I have some titanium rods, screws and a metal cage (Lumbar Fusion) in my back, and I'm going for an MRI at the end of the month. I'm curious as to how the titanium rods will distort the images and will be we able to tell if the discs above or below the fusion are herniated? Is there another type of "scan" that will be able to see the adjacent vertabrae if the MRI won't work?

Thanks
james
 

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Titanium is like aluminium anti-magnetic normally, but in a 3 tesla machine aluminium shows some kind of magnetic resistance

if you put something in aluminium in a angle of 45° it stays in the same position or falls down really slowly not like it normally should do

so before you go into the scanner i would seriously go speak with the doctor before entering the machine ;-)




Nobody with experience for standard G-shocks in an MRI room?
 

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That's good to know. So the machine won't tear the rods out of my body, but I might feel a slight tug :)

Titanium is like aluminium anti-magnetic normally, but in a 3 tesla machine aluminium shows some kind of magnetic resistance

if you put something in aluminium in a angle of 45° it stays in the same position or falls down really slowly not like it normally should do

so before you go into the scanner i would seriously go speak with the doctor before entering the machine ;-)




Nobody with experience for standard G-shocks in an MRI room?
 

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I'm working for air products and fill MRI's with Helium

are you sure that a g-shock is resistant to 3 tesla machines i have the DW-5600E and a G-7800B

I have never worked on a 3 Tesla scanner, but My G-shocks, including a DW-5600E are all fine at 1.5T with no problems.
 

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Mr_Pacman said:
Totally off topic here, but can anyone who is an MRI tech perhaps PM me as I have a question. I have some titanium rods, screws and a metal cage (Lumbar Fusion) in my back, and I'm going for an MRI at the end of the month. I'm curious as to how the titanium rods will distort the images and will be we able to tell if the discs above or below the fusion are herniated? Is there another type of "scan" that will be able to see the adjacent vertabrae if the MRI won't work?

Thanks
james
There is more to MRI machines than "just" the big magnet and its field and I strongly recommend you discuss your Ti reinforcement with the people at the MRI-facility. To get an idea what might happen: stick a piece of titanium in your microwave and switch it on ...... I do not know the operating frequency of the high-field medical MRI scanners and I do also not know how much power they put out (compared to a micro-wave), but I've come across several articles mentioning RF-heat as a safety risk / concern.

In your case, a CT scan might be a better solution (depends on what it is they want / need to image). These use X-ray radiation and technology.

Good luck with your scan, be it MRI or otherwise.

RonB
 

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Really, the only type of watches that could withstand one ( within reason ) is a G-Shock.
The Rolex Milgauss actually has a weak rating, so isn't suitable for the job!

cheers.
 

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Really, the only type of watches that could withstand one ( within reason ) is a G-Shock.
The Rolex Milgauss actually has a weak rating, so isn't suitable for the job!

cheers.
I didn't know that... what are the "ratings" as you say for the Milgauss and the/a G-Shock?
 

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The rating for the Milgauss is 1000 gauss, and the rating for the G-Shock I am not sure of, but one user says his G-Shocks have all survived 1.5 T ( 15000 gauss ) thus this reasoning makes the G-Shock a more suitable watch.

cheers.
 

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The rating for the Milgauss is 1000 gauss, and the rating for the G-Shock I am not sure of, but one user ( bmack325 ) says his G-Shocks have all survived 1.5 T ( 15000 gauss ) thus this reasoning makes the G-Shock a more suitable watch.

cheers.
Yeah, you might want to check what you're basing your "reasoning" on ; ) (I wouldn't be basing any decisions about my watches on hearsay/single anecdotes). Not really any evidence for proof of your conclusion in there.
 

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but I've come across several articles mentioning RF-heat as a safety risk / concern.
I have a pacemaker implanted, and my understanding is that the main reason I can NEVER have another MRI is because the tips of the leads that are screwed to the muscles inside my heart would heat up and burn the muscles. Probably not a good thing.... :)
(if they have to install new leads they just leave the old ones in, there's no safe way to remove them as far as I know)
 
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