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Comment by dsnr | Hacker News Reader

> That's why we don't give MRI's out the wazoo

Why? What are the risks of MRIs without contrast?

The biggest risk is false findings for a lot of diagnostic procedures. A false finding may cause enormous psychological stress, but more importantly it usually causes further, more invasive testing, which may pose much higher risks than the original procedure did. It's real statistical risk, which individual patients emotionally often can't relate to. Eg. an MRI shows clear signs of a tumor, you consequently get an endoscopic biopsy through your stomach, or colon, and then happen to die from anesthesia, intestinal perforation, sepsis... The "tumor" turned out to be a cryptic but harmless extra intestinal loop. Sounds made up, but this sort of thing happens enough to make unnecessary diagnostic procedures more harmful than beneficial.

However, I do think the reason MRI aren't used more often is because they are fucking expensive to operate. They need to run more or less 24/7 to be economical, which means they are commonly not scheduled with slack for "optional" investigations.

Or biopsy goes fine, turns benign but something malignant grows from the scar tissue from the biopsy

Not sure, if that's a reasonable possibility, but it's kind of irrelevant, since I would still consider a detected benign tumor a true positive for an MRI scan.

MRIs involve very powerful magnets and inattention around them has led to several widely-publicized deaths.

They’re also loud and can give patients a sense of claustrophobia or panic.

The reason is cost and availability, not risk.

Incorrect, there is risk associated with performing MRIs without chief complaints.

These types of MRIs often cause anxiety and can lead to riskier medical procedures that are not necessary. This is because imaging is actually not perfect. There is always a risk you see something there that is not a big deal, or that you misinterpret the image. That potentially means unnecessary surgery or medicine. That can kill you.

That's why if you go to any doctor in the US and say "I want an MRI, no, nothing is currently wrong with me" they won't do it.

I do not buy this argument. The error would be in misinterpreting the image and taking the unnecessary treatment, not in doing the test in the first place. How is there any benefit in having less information?

It's not an argument, it's just true.

In medicine, there is obviously a benefit in having less data. If I told you that you have a vein in your brain that could aneurysm at any point and instantly kill you, but no, we can't do anything about that - would that help you?

No, that would exclusively make your life worse, at least for the vast majority of people. It's also true for a lot of people. It could be true for you, right now.

Also, just because the error is in interpreting DOES NOT mean that the MRI is somehow magically off the hook. The risk came from the MRI. If you never did the MRI, then it would be impossible for that scenario to happen. That's just plainly true.

So therefore, if you do the MRI, there is a risk of that happening. Taking that risk without any complaints is deemed not worth it, so we don't do it.

> I do not buy this argument. The error would be in misinterpreting the image and taking the unnecessary treatment, not in doing the test in the first place. How is there any benefit in having less information?

There is no 'perfect information' but instead there is noise with every signal. It feels like that shouldn't be true ('the picture shows exactly what is happening, right?') but there are several levels at which the 'truth' that is assessed in an MRI can be degraded that have nothing to do with misinterpretation.

Even 'misinterpretation' is tricky - if something is only sometimes going to cause a clinically bad outcome, commenting or not commenting isn't a question of interpretation but of personal practice standards.

It’s definitely an imperfect signal, but we are capable of making decisions under conditions of noise and uncertainty. In other fields we would quantify the uncertainty, the consequences of making the error in either direction, and then act accordingly.

As a thought experiment, if MRI was as cheap and fast as testing blood pressure, do you think they’d still be given as rarely?

I think if we had a perfect tool where you can get MRI (and CT) data in the time it takes to get a blood pressure reading, it would only be used to detect slam-dunk diagnoses for further screening which is how we use blood pressure.

You’re assuming that we would skip this step, implicitly.

Now when would we do further screening? In a Bayesian framework, when we have a certain pre-test probability that we think we can improve to our desired level of post-test probability in order to take an action.

The fact that this is all automated doesn’t change our uncertainty about whether borderline calls should be targeted. Indeed, we’ll likely have more stringent criteria about things to ignore than are used today, and that may be worse for the small number of times we currently catch an actionable incidental finding.

And we’re not even beginning to consider cost, resource misuse, and the risks we’re incurring (an MRI machine isn’t safe to be around and costs a lot to maintain)

Edit: the things that kill people are smoking, heart disease, lack of exercise and poor diet. Targeting these is so much more useful than detecting a larger number of incidental findings

With a couple of exceptions, MRI screening of ‘worried well’ populations causes more harm than good.

https://www.linkedin.com/posts/gunnmartin_ranzcr-activity-72...

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