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Comment by mgraczyk | Hacker News Reader

Great document? I just read the entire thing, it contains no evidence or justification for their claims.

> We can then scan people with problems rather than people with too much money.

Right, this is what it's really about. MRIs are a scare resource and providers need to manage cost. Fortunately I can afford to pay out of pocket, but I'm just annoyed that doctors are so irrational about this

To be clear, it's up to a doctor whether or not to do a "needless biopsy". That has nothing to do with a scan.

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… they do it based on the scan result.

Avoiding a biopsy that wasn’t needed is a good thing.

You're imagining that the doctor is required to act irrationally or against the patient's interest. I understand that they do act this way, but I'm pointing out that they don't have to!

You walk into a doctor's office and meet for the first time.

Case 1. You have 3 full body MRIs taken 6 months apart in hand and give them to your doctor. Nobody has opened or looked at the scans yet.

Case 2. You do not have a scan yet

You are claiming case 1 will lead to worse outcomes in expectation. I claim that's impossible because the doctor can simply do the following: Without opening the scans, email them to the world's best radiologist. Tell that radiologist "only reply if it is nearly certain the patient has an operable cancer with the information available"

Now there are 4 possibilities.

Case 1 without cancer: nothing happens

Case 2 without cancer: nothing happens

Case 1 with cancer: you maybe survive

Case 2 with cancer: you die

The only reasonable objection to this is "that's expensive"

A whole body MRI is low resolution and thick slices, they are crap.

Instead you could get thin slices at high resolution of a body site that has issues or is suspected to have them. Do that instead.

Whole body MR is 5-8mm thick slices at low in-plane resolution. A whole body scan has about 512 pixels over a 50-60cm field of view. Usually it’s even less pixels than this.

Something like a knee, or brain is 2-3mm slices, and high in-plane resolution. A knee is 512 or even 720 pixels over 14cm. It’s vastly better. The difference is stark.

A liver scan or other abdominal organ is lower resolution than a joint or brain, but unlike whole body MR is scanned in multiple planes with multiple image weighting (t1 in/out/fat sat, diffusion, t2, t2fs, gadolinium contrast). A liver scan has thin slices.

Whole body scans generally do two coronal images (stir and t1) then call it quits.

Yes the machines should definitely get better, but I recommend you do get it if the cost it truly zero. Based on the data in the article it is still worth it despite the low resolution!

Sorry, I edited my above comment to remove references to myself.

For clarity, I’m an MR tech and I can get scans of myself if I want to.

I generally don’t scan myself as it gets messy fast. If I had concerns and for some reason couldn’t get a proper imaging referral, I’d get a scan with small, good coils with high element counts (not body coils like whole body imaging uses) and scan individuals body regions.

It is not only money, machines and doctors are also a limited resource.

The other bit is that no one follows your protocol, everyone looks at the scans, finds reasons to worry. Then you have the choice between unnecessary biopsies and psychological stress.

I agree, and I think rationing is the correct thing to do. I just don't like being gaslit by doctors (or would prefer doctors who know better).

And I agree most doctors won't do this, but again I blame the doctors and their training

I kinda agree with you and I understand your point but I also think there is a social-ethical reality that if a doctor finds something they must treat it. The two options are 1. doing nothing, or 2. reducing cancer risk and you get unnecessary biopsies.

You're thinking of this as there being an objective positive utility for not dying of cancer and a objective negative utility for biopsies, and there being an objective optimal "rational" tradeoff that the best radiologist can optimize for to get their "nearly certain" detection threshold.

But frankly - the tradeoff for the value of a human life is perhaps the most uncertain thing one could choose. It lies in the eyes of the patient if the worry and time associated with a false detection is worth their reduced chance of death. The ethical uncertainty expressed in the OP - are these unnecessary biopsies worth it - is warranted.

You a-priori do not know if you have cancer. The case 1 branches are:

Case 1 without cancer: you're a guy that knows more than doctors because you're the "I have 3 scans on hand guy", so as soon as you open the scans and the doctor says there's a mass, you will say 'OK what can we do???' And then you had a worthless biopsy.

Case 1 with cancer: you saved the 1 week it would take to schedule the new scan and get results and you're basically in the same situation except one week earlier.

That's not how it works. Without the history of scans spaced out in time, they would typically need a biopsy. Multiple scans over time shows change and growth and improves the likelihood of an accurate triage

And for the first part that doesn't happen in my scenario before the doctor doesn't look at the scans

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