General > General Technical Chat
I got exposed to toxic material of a thermometer...
Veteran68:
--- Quote from: HighVoltage on August 23, 2023, 09:28:33 am ---Would be interesting, if you ever need an MRI and the tiny beads would still show up.
--- End quote ---
I just cringed when I thought about how magnetic mercury might be (fortunately, not very, at room temp).
TimFox:
Like most normal metals, mercury is slightly diamagnetic (negative permeability) at room temperature.
However, non-magnetic conductors do show up on MRI scans since they "mess up" the local RF field, along with the small diamagnetic effect on the magnetic field.
Many metal surgical implants are now made from titanium to avoid injury from the strong magnetic field in MRI, and because titanium works well with bones in situ.
Veteran68:
--- Quote from: TimFox on August 23, 2023, 03:56:25 pm ---Many metal surgical implants are now made from titanium to avoid injury from the strong magnetic field in MRI, and because titanium works well with bones in situ.
--- End quote ---
I'm crossing my fingers that holds true in case I ever need an MRI, considering I have three titanium plates and 36 titanium screws holding my sternum together. :)
TimFox:
I worked for a while in MRI when the procedure was quite new.
We heard horror stories about older surgical implants made from ferromagnetic material, done before MRI was available.
The worst one I remember was an "aneurysm clip", a kind of spring clip to clamp a failed blood vessel to keep it from bleeding.
The torque applied to the long clip in the static field pulled it away from the blood vessel, killing the patient.
Another contraindication for MRI is an implanted cardiac pacemaker: some new ones can work (be very careful), but at that earlier time they contained a magnetic switch so that the physician could switch from synchronized to clock timing with a reasonable external permanent magnet for diagnostic purposes.
Also, the pulsed gradient and RF fields really screwed up the pulsing, leading to far too high pulse frequency.
One simple experiment put a normal pacemaker in a beaker of saline solution, inserted it into the scanner on the patient couch, and saw it run away at very high pulse rate.
"Nonmagnetic" stainless steels are not quite: titanium is very nonmagnetic (slightly diamagnetic).
Veteran68:
I still set off metal detectors! LOL
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