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Comment by AnthonBerg | Hacker News Reader

My favorite – this is to some degree my interpretation though! – my favorite is the default mode network, a kind of constellation of brain activity.

It’s called the default mode network because they found it through magnetic resonance imaging or something like this, and this activity pattern was the first pattern they saw!… A-ha! This is the default mode network! The default! The default mode! Yes!… the activity pattern in the brain of a human who has been persuaded to go into a very tight-fitting tube and is there all alone and it’s not pleasant.

The default mode is activated during introspection and social isolation and among the things it does is generate the sensation of being something which is distinctly not part of the rest of the world.

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I'm not one to typically have strong fear/anxiety responses in situations that aren't actually dangerous. However, I felt extremely uncomfortable being partially inserted into an MRI tube for a lower body scan. I couldn't imagine being shoved head first into that thing without being heavily sedated or completely knocked out.

I had a head MRI and my main anxiety involved praying to any powers that be that my tooth crown was truly non magnetic.

Sweet Lord, that is a white hot fear. When you remember the really old metal filling you have right before the machine kicks on.

The thought crossed my mind, to be sure! I talked about all that with the techs beforehand. "Are you sure this isn't going to yank my teeth out?" "Pretty sure. Now stop moving around."

They put metal detectors even in schools these days, can't they put one before the MRI lab?

I have permanent braces attached to the back of my teeth. I know they're magnetic, i can feel a slight pull if i hold a magnet close to them.

I don't know what i'll do if i ever need an MRI, otherwise i'd probably just find it cozy..

I have a simple hiatal hernia. One of the treatment options is to basically put a weighted band around your esophagus above the stomach so that the weight holds everything downward so your stomach doesn't get pulled up through the hernia. I imagined being in a car accident or some other situation where I'm nonresponsive, the doctor ordering an MRI, and me re-enacting the scene from Alien. Nah, I'll take my chances with the hernia, thanks.

Well - if it helps any - my understanding is that a doctor at an ER center would order a CT scan which is based on x-rays and can be done in a matter of a few minutes.

MRI scans are really reserved for things that don't image well on CT scans or when the resolution of a CT scan just isn't good enough. They also take quite a bit of time to perform.

I feel uncomfortable around x-ray rooms. Can humans feel radiation or I am making it up?

Humans cannot feel x-rays in the dosages you'd experience in an x-ray room. A sufficiently powerful x-ray would feel hot the same way a bright light does.

The mandatory shielding around these rooms is robust. I shadowed a technician inspecting a newly fitted x-ray room and observed the very sensitive equipment used to verify absence of leakage. There was a small puncture in the lead shielding that was quickly found and resulted in a delay until patched.

I don't know what you mean by "around" but if you mean walking down the hallway outside the x-ray room, my guess it's the low frequency sound these machines often produce that you're reacting to and not x-rays themselves. Not to mention the almost sci-fi signage alerting your brain to danger.

And inside the shielding envelope, modern x-ray equipment is still at very low levels unless you're the patient (and even as the patient, imaging requires much lower levels than in the past).

Could be a million things you subconsciously notice.

* the warning signage

* things that are related to the lead shielding (micro changes in gravity, smell of lead salts, ...)

* infrasound caused by the machinery

* people waiting for an x-ray around who are less-than-happy...

The problem with this kind of thing is that it is often highly individual, and barely, if all measurable with our current scientific instruments. Some people keep claiming that humans are incapable of even hearing infrasound, or sense gravity, claiming anyone who can sense them is spreading new-age esoteric nonsense or is mentally ill. See also: Electrosensitivity.

I'm not saying these things do or do not exist, just that it is in the realm of possibility.

Does it make break down oxygen into ozone ? If it does maybe some people smell it

I wouldn't worry much as an X-ray recipient. There was talk in the 1950s about the trade off of getting a routine chest X-ray, say to check if you have pneumonia if you see your doc about a respiratory infection, vs a hypothetical risk of cancer.

Today X-ray dosages are way less because they use

https://en.wikipedia.org/wiki/Digital_radiography

so I wouldn't be afraid to get one. The radiology technician though needs to take special precautions because they are around it all day. Personally I would avoid a CAT scan if it were feasible

https://en.wikipedia.org/wiki/CT_scan#Adverse_effects

Nah, energy is way too low. If they emitted enough for you to feel it you'd be dead in a week.

I certainly felt my last MRI though. New machine, so probably high powered. Abdominal/liver MRI. Every time the RF was on I could feel a gentle warmth throughout my midsection. Weird but cool.

I don't really mind medical procedures like that. The time I got punched at Elephant Butte Lake and got stitches at the emergency room I went into a deeply relaxed state that scared the nurse because she thought I'd fallen asleep. Even the noise of an MRI machine is not that startling if you know it is coming.

Indeed. I have a brain tumor (not cancerous and controlled by medication) and for a few years after diagnosis I had to get MRI's every few months for the first year, then one every year for a few years. It was a bit nerve wracking the first couple times but now I can fall asleep in those machines lol.

During my MSc I spent a total of more than 25 hours being scanned in an MRI machine for a study investigating the neurobiology of reading, and by the end of the study I was so relaxed in there that my main problem was not falling asleep because I was lying down with repetitive noises around me!

this is so interesting.

it’s not the first nor the last time wish that communities would not refrain from changing terminology. fitness is as important as accuracy and we shouldn’t be wary of dropping such inaccuracies, especially when they bring such strong connotations.

For one thing the technology in an MRI based on a phenomenon known as nuclear magnetic resonance

https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance

they dropped the "nuclear" bit because it is scary, it doesn't involve any ionizing radiation. It is all about making the nucleus wobble but not about splitting atoms. I have fond memories of doing NMR experiments in senior labs as a physics major.

So this activity pattern could actually be the claustrophobia mode network?

Or "questioning the life decisions that led to finding myself in this situation" mode network?

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