Type of RFID chips used for DMS?

DMS General
#21

As a EE, physician, hacker who works in MRI frequently I can tell you a couple of things.

  1. The magnets are 3T these days and that alone seems to disable some RFID chips but I’m not sure how that happens. I’ve had several badges disabled when I forgot to remove them. Perhaps it either magnetizes a core in an antennae or induces a destructive current in a critical component.

  2. A fairly high power RF signal is pinged onto the pt to flip protons within the pt under the magnetic field. This signal alone can destroy components in the same way that a microwave would do the same.

The machine listens for the resultant RF signal resulting from the protons flipping back to neutral. That’s how imaging takes place. Only certain tissue is in the right micro magnetic environment to respond at any moment in time as the mag field is tweaked by a separate coil millisec to millisec to select the tissue in 3d space.*

  1. There is an MRI screening protocol for patients that covers anything that could be a problem. I would guarantee that you would not get anywhere near the MRI machine with an implanted chip or anything else that they don’t fully understand. Stuff like that can heat up. In fact the pt experiences warmth over an extended time just from the RF although it’s apparently not destructive in any way. Any virtual loop created by patient tissue (ex hands touching legs creates a loop between the body and the arm or space between legs if feet are touching) can cause unwanted EMF and resistive heating. Thus positioning with padding is done carefully for an MRI.

BTW, the big magnet is always on and is a hazard to devices. RF and modulator magnet coils are only on when scanning.

RF technology changes. If you are serious, I would not recommend an implanted chip although you could always remove it. But if you are serious about it and they want a fortune to implant one, I could implant it safely with plenty of waivers of course!! :fearful: We could even have a minor surgery clinic / diy class at DMS to demonstrate.

There is a bonafide med school radiologist member at DMS and it’s not me. Don’t remember his name.

*bonus material

1 Like
#22

Badge antenna are different (large flat coil) from a small RFID chip antenna and conduct RF and magnetic fields differently. I had an MRI recently with an RFID implant in my hand and while I did warm up, my hand where the chip was didn’t warm up any more than the rest of my body (to be fair, I haven’t had an MRI from before the implant) and I did inform the technician about the chip before the scan (they raised no objections about it, mainly due to the size it seems). Also, there has been a RFID implant “class” at the Makerspace and they got a body mod artist to do the implants (if I remember correctly, it was about $75 total for the chip and the implant procedure). More info on RFID implants and MRIs (including sources and studies): https://forum.dangerousthings.com/t/x-series-implantable-transponder-faq/28#faq-mri

-the purring dork

#23

Cool, I did not know they were OK in the MRI. At Baylor they are paranoid about anything different going into the MRI. Agree, they won’t get ‘ripped out’. It is a powerful magnet but we often accidentally bring things into MRI that don’t belong there, typically small things like badges and pens. They might torque around a bit but the force isn’t that great. The real disaster is bringing in something like an incompatible O2 tank or IV pole.