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0 pointsriahi2y ago0 comments

The RF pulses and field gradients can directly stimulate the peripheral nerves. I have had involuntary muscle twitching triggered by many pulse sequences. It’s not unheard of. It made me more sympathetic for patients who have motion in images. It could be that the particular combination of pulse sequence and their nerves don’t jive and triggers movement.

Source: Radiologist (and personal experience in the bore)

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lostlogin1y ago

If the patient isn’t twitching occasionally, the resolution is too low. We aim to be just below peripheral nerve stimulation threshold.

I’m sort of joking, but if you aren’t ever getting PNS, the machine is not being run very hard.

However the sensation you get in the region being scanned feels more like heating than PNS to me. You notice it more on high SAR sequences, suggesting that might be the cause. PNS just feels like twitching you can’t control, but ones milage may vary as this is anecdotal.

Source: MR radiographer.

riahiOP1y ago

I don’t think it’s heating. I think it’s PNS because my leg will periodically twitch which I can time with the pulse sequence.

I also have some small ACL reconstruction hardware in the knee which might interact and predispose that leg to moving…

I am well acquainted with high SAR abdominal scans in a 3T from my time doing scan certification in a petmr. Even though I “know” that tissue heating from high SAR is a thing, it always surprises me when my abdomen gets warm.

lostlogin1y ago

I used a high spec Siemens Avanto which a University owned. We used to get people complaining about PNS in the left hip and just above the bridge of the nose. It was a weird thing, and mainly happened on cardiac scans. Some found it too painful to continue with scanning.

I’ve had a little bit of PNS, but nothing that strong.

The SAR sensation of being heated from the inside is an unusual one, I’m not sure I’ve had anything else do that?

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0 pointsriahi2y ago0 comments

Source: Radiologist (and personal experience in the bore)

0 comments

lostlogin1y ago

If the patient isn’t twitching occasionally, the resolution is too low. We aim to be just below peripheral nerve stimulation threshold.

I’m sort of joking, but if you aren’t ever getting PNS, the machine is not being run very hard.

Source: MR radiographer.

riahiOP1y ago

I don’t think it’s heating. I think it’s PNS because my leg will periodically twitch which I can time with the pulse sequence.

I also have some small ACL reconstruction hardware in the knee which might interact and predispose that leg to moving…

lostlogin1y ago

I’ve had a little bit of PNS, but nothing that strong.

The SAR sensation of being heated from the inside is an unusual one, I’m not sure I’ve had anything else do that?

j / k navigate · click thread line to collapse