Safety: Torque due gradients and main field

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motoca
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Joined: Tue Jul 17, 2012 2:41 pm

Safety: Torque due gradients and main field

Post by motoca » Tue Nov 05, 2013 3:20 pm

Hi all,
I know that if you put a ferromagnetic material inside a MR bore, it suffers a torque or missile effect.
I know too that gradients can cause peripheral nerve stimulation and RF pulses are responsibile mainly to "heat tissues".Gradients are about miliTesla while B0 is about Tesla.
OK, after a brief introduction about I know about MR safety, I have "two" doubts:

1) Is there any torque due gradients field too? Or B0 is so huge that the gradients can't apply a additional shift in those materials? If they cause torque, Have I worry about it in in relation to patient safety as I have to have with B0 torques?
2) Do gradients cause any (a little) heat in tissues too or only RF pulses cause it?
Thanks in advance
Motoca

Dave Higgins
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Re: Safety: Torque due gradients and main field

Post by Dave Higgins » Thu Dec 19, 2013 3:53 pm

For practical purposes, you can ignore gradient fields for torque and missile effects.
Similarly for heating effects, the RF field need only be considered.

Dave

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