Why are MRI machines so expensive to operate?

[sophiecentaur]

Why would people go to the effort of building simpler, less expensive, portable MRIs for remote or third world use if ultrasound was as effective in most cases?

Two comments here. firstly, it appears that a portable MRI scanner can be ten times the cost of an ultrasound unit. Secondly, I can't find any references to portable MRI scanners earlier than 2023 - so it's new tech. Maybe, in a few years' time, things will be different.

Meanwhile, every (?) woman in the UK has access to an ultrasound scan and it can be done on a home visit. How many women are given an MRI scan for a routine progress scan? ultrasound has proved its worth. There is rightly a strong resistance to arbitrary changes in medicine but ultrasound is gaining ground in its use for examinations of soft tissue.

Maybe we'll get a comment from someone with real experience of imaging???

 

[JT Smith]

Maybe we'll get a comment from someone with real experience of imaging???

That would be best since neither of us really knows what we're talking about.

A quick perusal of the web suggests that ultrasound doesn't work as well when bone or gas filled organs are in the way. Probably it's more complicated than just that.

FWIW, I've had one MRI and one ultrasound, both at the same clinic. The MRI was for looking at my shoulder joint and the ultrasound was to examine organs in my abdomen.

 

[Greg Bernhardt]

It's not gonna say it like that of course but CT scans can be equivalent to 3 years of background radiation. Not a huge deal if you just do one or two, but if you need to do a lot it's not great.

What about at the dentist? I get one for my teeth/jaw every year.

 

[f95toli]

Two comments here. firstly, it appears that a portable MRI scanner can be ten times the cost of an ultrasound unit. Secondly, I can't find any references to portable MRI scanners earlier than 2023 - so it's new tech. Maybe, in a few years' time, things will be different.

It depends on what you mean by "portable". Low-field MRI has been under development for quite a long time. Because the fields are lower they can be generated using normal magnets; meaning you remove the need for superconducting magnets. Even if the rest of the system requires cooling (because e.g., SQUIDs are used) this should be a substantial saving.
However, low-field MRI does not -as far as I know- have the resolution of regular MRI (there are some intrinsic limitation simply because lower fields mean lower polarisation). It might still be useful for some medial imagining, but last I heard (conference talk a couple of years ago) the "killer app" was no longer in medicine, but in explosives detection, that is for use in scanners of large items at e.g. checkpoints

I don't know how much of the cost of an MRI machine have to do with cooling. I suspect it is not nearly as much as people think. A "basic" 4K cryogenic system of the type that is used for MRI (with compressor and cold-head is something like £80,000 from Sumitomo or Cryomech; that is not very much compared to the cost of the whole system

 

[Vanadium 50]

If somebody needs multiple full-body CT scans, they probably have more immediate problems than an elevated risk for cancer some years down the road.

By the same token, we could require ambulances to travel only on side streets at no more than 15 mph and obey all traffic signs and signals, to reduce the chance of an accident. But we don't.

 

[Vanadium 50]

What about at the dentist?

Your dentist gives you a full body CAT scan? Um..where exactly do you have your teeth growing?

 

[gleem]

I can't find any references to portable MRI scanners earlier than 2023 - so it's new tech. Maybe, in a few years' time, things will be different.

Portable MRIs are designed for small fields of view applications like the brain/ face, knee/ankle/foot or elbow/wrist/hand so their application is limited. These are low-field ( 0.065Tesla) devices and as such have poorer image quality.

Transportable whole-body MRIs for temporary use or as a rented instrument have been available almost from their initial clinical introduction. They can be fit into an ordinary house-sized trailer and moved and set up in a day. Rural hospitals often opt for such a service.

 

[sophiecentaur]

Transportable whole-body MRIs for temporary use or as a rented instrument have been available almost from their initial clinical introduction. They can be fit into an ordinary house-sized trailer and moved and set up in a day. Rural hospitals often opt for such a service.

That figures. You just can't get high fields without a big installation. It definitely comes under the heading 'transportable' . The cost would still be high.
The applications you mention are not so good for ultrasound.

 

[russ_watters]

What about at the dentist? I get one for my teeth/jaw every year.

I found this:
https://www.francismccarthydmd.com/...radiation-risks-the-truth-about-dental-x-rays

At .005 mSv, the radiation you receive from the aforementioned dental x-ray is less than 1.6% of your daily background radiation exposure. You are exposed to the same level of radiation just from sunlight each day. Additionally, each x-ray is an individual dose rather than constant exposure, which is another factor in the cancer risks of radiation exposure. X-rays only increase the odds of dying of cancer by 1 in 2,000; compare this to the natural 1 in 5 chance you have of dying of cancer.

That's not as reassuring as they seem to want it to sound. 1.6% of background doesn't sound like a lot, but it's all focused on a very small area. 1 in 2,000 added risk of death is about the same odds as 500 skydives. That sounds like a lot to me. And is that per x-ray or total from 75 years of annual x-rays? Sounds like per x-ray.

There's also this:

The purpose of this review is to summarize the results of studies on of the association between exposure to dental X-rays and health risk....

In brain tumor studies, the association between dental X-ray exposure and meningioma was statistically significant in 5 of the 7 studies. In 4 of the 5 thyroid-related studies, there was a significant correlation with dental diagnostic X-rays. In studies on head and neck areas, tumors included laryngeal, parotid gland, and salivary gland cancers. There was also a statistically significant correlation between full-mouth X-rays and salivary gland cancer, but not parotid gland cancer. Health outcomes such as leukemia, low birth weight, cataracts, and thumb carcinomas were also reported. In a few studies examining health effects related to dental X-ray exposure, possibly increased risks of meningioma and thyroid cancer were suggested. More studies with a large population and prospective design are needed to elaborate these associations further.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6341170/

This is enough to make me wary of annual dental x-rays, but that's just me.

 

[Vanadium 50]

"More studies are needed" means "the effect is too small to see with the samples we have".

If 100% of people receiving dental x-rays developed oral cancer, we would know it immediately. If nobody (in a sample of N) got it, we'd know the probability was less than something like 3 or 4/N. You can't prove it iz zero.

As it stands, about 1% of the population develops oral cancer. The risk is ~5X higher in smokers. That sets the scale for how big a risk x-rays are: if it were much bigger than a fraction of a percent, we would already know. If it is a part per million, we probably wouldn't.

You know the lead apron you put on? It helps - but not for the reason you think. The number of x-rays it blocks isn't that different from the number that scatter back in. However, it minimizes patient movement, so it reduces the probability that you need to take a second set because the patient wiggled.

 

[gleem]

However, you’re always exposed to ionizing radiation. On average, your body is exposed to 3.1 millisieverts (mSv) of natural radiation alone per year. At .005 mSv, the radiation you receive from the aforementioned dental x-ray is less than 1.6% of your daily background radiation exposure.

@russ_watters

Check the math .005mSv/3.1 mSv = .0016 = 0.16%

 

[AndreasC]

What about at the dentist? I get one for my teeth/jaw every year.

A basic X-ray and a CAT scan are not the same! If you are getting the first, the dose is minuscule.

 

[Vanadium 50]

You just can't get high fields without a big installation

You can get to about 0.3 T with ferrites (permanent magnets) although 0.1 T is a lot cheaper and easier to find. You can get to 1 T with rare earth magnets, but I shudder to think of the cost.

My primary concern would be safety - that's a lot of field that you can't turn off. I would also want to see plenty of margin in the return yoke.

 

[russ_watters]

Check the math .005mSv/3.1 mSv = .0016 = 0.16%

Yeah, they really bungled that, and it's worse than what you are saying. Googling around a bit, those are the numbers (they vary some, of course). But it's 3.1 per year and 0.05 per x-ray and they were looking for percent per x-ray compared to per day. .005/(3.1/365) = 0.59 (59% of daily exposure). It's less than an airline flight, but again, more concentrated.

 

[russ_watters]

"More studies are needed" means "the effect is too small to see with the samples we have".

If 100% of people receiving dental x-rays developed oral cancer, we would know it immediately. If nobody (in a sample of N) got it, we'd know the probability was less than something like 3 or 4/N. You can't prove it is zero.

It's trying to separate a weak signal from a strong signal. I get that that's difficult to do, but isn't very re-assuring to me either.

The 1/2,000 prediction appears to come from studies cited here:

Some studies have estimated the risk of radiation exposure from imaging tests based on the risks from similar amounts of radiation exposure in the studies of the atomic bomb survivors. Based on these studies, the US Food and Drug Administration (FDA) estimates that exposure to 10 millisieverts (mSv) from an imaging test would be expected to increase the risk of death from cancer by about 1 chance in 2,000.

https://www.cancer.org/cancer/risk-...ays/do-xrays-and-gamma-rays-cause-cancer.html

But that's the linear, no threshold model, which is itself somewhat controversial (which doesn't mean it isn't accurate).

[edit] And 10 mSv isn't 0.05 - different tests. That would seem to drop the risk by a factor of 200. Sorry, that first source wasn't good.

 

[Greg Bernhardt]

A basic X-ray and a CAT scan are not the same! If you are getting the first, the dose is minuscule.

oh gosh, you're right, it's an x-ray, a long day

 

[Laroxe]

I think Gleem makes a lot of good points, but overall I suspect the best answer to all of these issues is, "who knows". Over time, all of the various scanner technologies have been improving, the machines are more efficient, more sensitive, generally smaller, becoming more common/available and so overall it's getting cheaper. This also has an impact on the radiation doses used, this is an issue which is given a high priority, though whether this is justified is unclear. It is assumed that any dose of radiation carries some risk, but a great deal of the evidence to support this still comes from survivors of the A bombs. A great deal of what is in the literature is poorly supported and likely to be obsolete.

It's important to recognise that the various scanners provide different information and are not easily interchangeable, the best type of scan is guided by what the clinicians are looking for. The dose delivered can be very variable, depending on the scan detail and the areas covered. The risks are also very variable, as there are significant individual differences in people's sensitivity and in the type of tissue exposed. It is suggested that a dose of 10 millisieverts (mSv) might be associated with a 1 in 2000 risk of a malignancy, this should be compared to the lifetime risk of 1 in 5 for the development of cancer.

All of these scanning technologies, even when used correctly, require careful evaluation by experts and lately by AI systems, it can be very difficult to make accurate diagnosis based on scans, results that are unclear often lead to further investigations, or even risky treatment interventions. This is really the most significant threat associated with these diagnostic technologies, while they have made some powerful and very useful tools available to Dr's, Inappropriate or overzealous treatments do far more harm.

https://www.fda.gov/radiation-emitting-products/medical-x-ray-imaging/what-are-radiation-risks-ct

 

[sbrothy]

This is one of those scenarios that makes me glad I live in Denmark where healthcare is free and ubiquitous (read: included in taxes). On the other hand I sometimes have the distinct feeling that our MRIs, CAT-scanners - what have you - are second-rate for the exact same reasons. I have little to no evidence though.

One horror-story is that the machine that they use to ionize cancer on Copenhagen teaching hospital sometimes fall out of "whack". A patient told me that. Private hospitals have been offering to undertake a lot of operations to bring down the waiting lists (the news here reported one guy who have to wait 12 years (!) for a jaw operation to alleviate his migraines so he can do his job.) but the state wont let them for some reason. They allowed them to handle perhaps 13 out of 100. Of course I only know what I read and see in the news but I'm sincerely doubting our little "socialist paradise" here....

I know this is an old thread [EDIT: Oh not so old it would seem.) but I must admit that I stand corrected. I was CT-scanned myself very recently (doctors were worried about my lungs (everything seems to be fine though), and it was a very professional experience. The results were ready that same day; only hours later my physician had the results in his hand!

Also, even though my mum had been diagnosed with what we all thought was terminal cancer (13cm high tumor in one of her lungs), which had had several years to metastasize (some of it to her brain even!), they now say they got it all! Allegedly she's completely hale!

I'm shocked! Positively shocked and impressed!

So I happily eat my words about the Danish healthcare system!

:)

[EDIT: Corrected spelling error s/metastase/metastasize. Hope that's correct.

 

[pinball1970]

I operated one in Manchester, pretty cool and learnt a lot as a grunt. An awful lot of guys in the team but they had other kit there too, IR, MS think.
The techs showing up one day to change the liquid He (I think) warranted a quick move to the far side of the lab to let them get on with it!
We did not put people in there (NMR) we put novel organics from the synthesis lab.