This means, for example, not necessarily performing a biopsy just because something is there (but it's probably benign). The cost of invasive procedures such as biopsies, and risk-increasing tests such as CT scans has to be balanced against their benefits.

Of course, there is no risk with a full-body MRI scan. The machine itself is expensive, but otherwise it nominally only costs electricity, maintenance and operation. If full-body scans were, as you say, routine, the cost of the machine would be amortised and an economy of scale should prevail.

The problem is legal; if a doctor sees something on a scan and doesn't take action, they can be sued. This is the case even if there is negative expected utility from performing the test due to the low probability of an actual malignant condition. Due to this, it is not uncommon to hear doctors say that full-body scans do more harm than good.

Until the legal system starts to account for rational choices based on statistical information, this problem is going to persist.

Not quite true. While the scan itself isn't harmful, the strong magnetic fields, RF fields and noise have caused several accidents, some fatal. Compare for example http://www.auntminnie.com/index.aspx?sec=sup_n&sub=mri&pag=d... "The FDA's Manufacturer and User Facility Device Experience (MAUDE) database documented a total of 40 incidents for MRI in 2004. In 2009, the total more than quadrupled, to 193 reported adverse events."

Example of a fatality: http://abcnews.go.com/US/story?id=92745

> False positives aren't inherently a problem. If you have accurate understanding of the sensitivity and specificity of a test, then you can take action to maximise the utility of the expected outcome.

False positives can still cause huge psychological strain on the involved person(s).

The legal system does account for this. To succeed in a malpractice action, a plaintiff must prove a defendant failed to meet the required standard of care, which means the defendant failed to exercise that degree of skill and learning ordinarily exercised under the same or similar circumstances by members of the defendant's profession.

If these "rational choices based on statistical information" you refer to are within the accepted standard of care, a doctor is not going to be successfully sued for doing so.

In many cases, the optimal action is not to test in the first place. "Overdiagnosed" is an interesting book on the subject by Dr. H. Gilbert Welch. A recent piece by him in the NYT gives an idea of his thesis: http://www.nytimes.com/2014/11/06/opinion/an-epidemic-of-thy...

That's not really true. The cost of the machine is amortised by having it be in use at all times. In my experience MRI's are already fully utilized. I've had 3 in the past year. Even during Diwali there was always someone immediately before and immediately after me, and I never have much choice about appointment times.

Google indicates you can pay up to $3M for a MRI machine and $100K/yr energy and required maint costs. Google indicates a median radiologist gets $300K/yr and to make the figures ridiculous I'll dedicate one radiologist full time to the MRI. Google indicates mean lifetime of a MRI machine is a decade. Google indicates a hospital remodel to make a MRI safe room and electrical and cooling and ventilation might exceed the cost of the machine maybe $4M. Google indicates budgeting 3 hours per patient is not totally unreasonable. There is maint downtime and testing and the radiologist probably wants to sleep occasionally, even if there are actual specific scans that only take 15 minutes.

So the total cost over the decade lifetime of a MRI machine

3e6 + 4e6 + 300e3 * 10 + 100e3 * 10

You don't need a calculator to add that up to a cool eleven million bucks for ten years of MRIs. However you divide that out and thats only three grand per day over that decade. Or if you assume a long term average of 3 hours per scan (a bit on the high side) thats $375 total cost per scan.

Google reports the average billing is somewhat under two grand, but my math shows about four hundred bucks. Even assuming only 50% utilization they can still only account for $800 per scan.

I'm thinking that despite the mantra / astroturf that MRI is really expensive to provide, its actually a huge profit center for a hospital. Not as bad as the proverbial $35 aspirin pill, but pretty profitable none the less.

Another way to run the numbers is if the fixed cost of having the machine and radiologist available is about $3K/day, and they get about $2K/scan in revenue, you may have been part of a long MRI train that day, but the average machine actually only scans 3 people every 2 days on long term average.

Sounds like a market that's either ready for disruption, or so well protected by regulation that it can't be disrupted.

A little bit of trying to find numbers suggests that 1 MRI machine might be feeding 20 doctors (if you've arranged for 56 scans a week to be the low end number and take into account specialization, this starts to make sense). I guess they are each spending a couple hours during many of their weeks.

You have labor at ~30% of cost, it looks like it should be more than 50%, and could easily be even more.

That's because I chose the highest possible machine price and highest possible room construction price I could find on google. Its quite possible an individual installation could get away with a merely average $2M machine and basically nil building remodeling costs, in which case the labor cost percentage would naturally dramatically increase.

I don't trust the google data I found of $100K yearly for energy and service contract. That sounds low. 10% of purchase price sounds believable for high tech devices.

I googled some MRI tech salary data and one tech for a decade is going to be $1M. So merely not installing marble and solid gold fixtures in the room would easily pay for a team of three full time techs and one radiologist doing absolutely nothing but supporting one machine. Which is pretty ridiculous, but I want to estimate high to make my overall conclusion strong.

None the less my overall conclusion stands that it would be a significant challenge to spend, both labor and capex, more than about a third of MRI sales price to provide the service. Looks like quite a nice profit center.

And false positives are not a rare event. False positives are very common.

On top of that the radiation (from CT scans) increase the risk of cancer.

Scans for healthy people are strongly discouraged.

There's a possible benefit if you have any of the genetic markers for lung cancer or are otherwise at risk of lung cancer - heavy lifelong smoker for example.

CT showed that it was pretty bad, que months of stressing and worrying about what was going to happen.

Turns out it was a false positive, caused by an accessory spleen looking like a tumour. False positives do happen, and they can be pretty devastating - it took quite a while for her to get back to normal.

Stressing and worrying are both several orders of magnitude better than suffering and dying.

Source: My case wasn't a false positive.

So now you have someone who thinks they have might lung cancer, when in fact they probably have almost harmless scars from chicken pox.

But what do you do if you think you have lung cancer? Do you go and get biopsies? The stress from that result is significant and shouldn't be dismissed as something trivial.

My point is people who went through the experience of having test results compatible with cancer and then discover it is just a false positive (which technically it's not even true, there's no cancer diagnosis before a biopsy, it just can't be excluded), well, these very people seem to speak out against screening, or adopting more extensive screening policies, because they had a "false positive", and "it's stressful".

I am pretty sure all the people whose lives were saved by screening find that pretty selfish.

The harm/good ratio of screening depends crucially of the false positive/negative ratio vs. the actual prevalence of the condition or disease being screened for. (Plus, obviously the psychological/medical "cost" of a false negative/positive.) I would recommend the talk at [1]. This particular issue is brought up about midway through the video, but I recommend watching the whole thing.

[1] http://www.ted.com/talks/peter_donnelly_shows_how_stats_fool...

Harms of Screening Mammography: http://www.cancer.gov/cancertopics/pdq/screening/breast/heal...

Sure, but if you're scanning daily (or close to it), then you don't need to do anything immediately for a positive. You see a growth that looks like it might be cancer—then have the doctor watch it. If you're scanning often, then you'll see any changes. Does it grow? Then it's something to be concerned about. Does it stay the same? Then you don't need to worry.

With frequent enough scans, finding something isn't a cause for any alarm. You can watch how it changes, and decide if it's a concern based on that. Like skin moles. Yes, they could be a problem, but if you have one, you don't need to worry unless it starts changing. Just having one doesn't cause anxiety.

I agree, and I'm not recommending we do that right now. But imagine if we had cheap, fast ways to do the scans. So much money is being pumped into cancer treatment right now, I'm just wondering if better cancer detection might be more beneficial. Our current treatment methods might get us a lot farther because we'd use them when the tumors are smaller, and we'd have a much better sense of how aggressive a tumor is.

[0] http://www.kurzweilai.net/new-lab-on-a-chip-could-revolution...

It's preventative health care, not "sick care".

http://www.cancer.org/cancer/cancercauses/radiationexposurea...

There's also the issue that, at present, MRI scans are considerably more expensive than CT.

Google for Esaote (my coworker got scanned a couple times by their product) and "extremity MRI"

As you'd imagine the economics are non-trivial. The machine is smaller and cheaper that a full size MRI (google claims its fraction of a million, like the cost of a house) but obviously something that can only scan knees and ankles and elbows is a pretty tough sell unless you're a sports medicine practice in which case its a pretty easy sell...

On the other hand if a "whole body sized" MRI costs $2500 per scan, then you've only got to scan maybe 100 knees to pay the capital cost of a dedicated extremity MRI. And how long would that take at a busy sports medicine practice, like a week?

I would not describe the machine as portable. Being a giant magnet you probably need a special safe room to operate it, so I don't envision paramedic/EMT ever having a MRI in the ambulance or whatever.

WRT discussion in the comments about claustrophobia I don't mind the small spaces so much as being chained down for an hour or so, that drives me nuts. My MiL went thru some tests for her gallbladder that took hours, I'd be clawing at the walls after ten minutes. Also if I could get nitrous for my wisdom teeth I see no obvious reason a MRI patient couldn't be gassed but they "never" seem to do that, which I find weird. For $2500 for a full body scan you could at least give me a couple shots of vodka.