The discussion revolves around the dangers of having metal in an MRI machine, particularly focusing on the effects of ferromagnetic and non-ferromagnetic metals in the context of magnetic resonance imaging. Participants explore the implications of metal presence in MRI environments, referencing both theoretical and anecdotal evidence.
Participants generally agree that ferromagnetic metals are hazardous in an MRI environment, while there is some debate about the risks associated with non-ferromagnetic metals and the effects of eddy currents. The discussion remains unresolved regarding the extent of risks posed by non-magnetic materials.
Limitations include the potential for confusion regarding the definitions of magnetic and non-magnetic metals, as well as the specific conditions under which eddy currents may cause effects. The discussion does not resolve the implications of these factors.
Jesse H. said:MRI stands for MAGNETIC resonance imaging.
http://en.wikipedia.org/wiki/Magnetic_resonance_imaging -First google result, second paragraph first line.
"An MRI scanner is a device in which the patient lies within a large, powerful magnet where the magnetic field is used to align the magnetization of some atomic nuclei in the body, and radio frequency magnetic fields are applied to systematically alter the alignment of this magnetization."
The metal is ferromagnetic. The same property that makes it so that magnets can stick on metal refrigerators. Just like there is a force exerted by a magnet on a refrigerator, there is also a force exerted by a MRI system on a ferromagnetic implant. Depending on the magnitude of that force and the strength and importance of the tissue nearby, the consequences can be disasterous.pa5tabear said:Ok. So what about the metal makes it respond to a magnetic field?
A six-year-old boy undergoing an MRI examination died after the machine's powerful magnet pulled a metal oxygen tank through the air, fracturing his skull.
an MRI magnet pulled a gun out of the hand of a police officer and the gun shot a round that lodged in a wall.
Even with non-ferromagnetic materials you can get forces due to eddy currents, but I have never heard of an injury due to this. It is kind of a cool effect to see, I used to show it to tour groups. I would take an aluminum safety sign, and try to wave it back and forth through the field, etc.Q_Goest said:For non-magnetic metals such as aluminum, copper, austenitic stainless steel, titanium, etc... there is no problem with having them near an MRI.
See the link about tattoos I posted:DaleSpam said:Even with non-ferromagnetic materials you can get forces due to eddy currents, but I have never heard of an injury due to this.
identified the cause as originating in a locally induced electric current. This can, generically speaking, be induced by any metal (not just ferromagnetic metals) moving through a high-frequency magnetic field
Read More: http://www.ajronline.org/doi/full/10.2214/AJR.06.5082
Iron Man is so screwed...BruceW said:soo... the take-away message is that magneto (from the x-men franchise) is a lot more dangerous than I had previously thought? hehe
Interesting. I do a lot of work for MRI manufacturers and as long as the materials we use for the equipment we design are non-magnetic such as austenitic stainless and aluminum, we have no problem with them. Does the effect you're mentioning only apply to things that are moving? All our equipment is generally stationary (or moving slowly) when connected to the MRI.DaleSpam said:Even with non-ferromagnetic materials you can get forces due to eddy currents, but I have never heard of an injury due to this. It is kind of a cool effect to see, I used to show it to tour groups. I would take an aluminum safety sign, and try to wave it back and forth through the field, etc.
Yes, only moving metal feels this force from the main field, and even then it is only significant on large sheets of metal where the induced eddy current loops are large. That is why I always use an aluminum sign.Q_Goest said:Interesting. I do a lot of work for MRI manufacturers and as long as the materials we use for the equipment we design are non-magnetic such as austenitic stainless and aluminum, we have no problem with them. Does the effect you're mentioning only apply to things that are moving? All our equipment is generally stationary (or moving slowly) when connected to the MRI.