Let's go all the way why not CT edition
January 27, 2017 3:09 PM   Subscribe

Had my first CT scan today... wondering why I can't just get a full body... does it increase the 'cost' that much?

Long story short I had an image order for a neck CT scan and it's done, yay! Except I left wondering why not just do a full body? Is the cost really that much more? I would think most of the cost was overhead and once I'm laying there and I've got the contrast flowing it couldn't be *that* much more to go ahead and do a full body. Not that I need one, just curious.
posted by one4themoment to Health & Fitness (19 answers total) 2 users marked this as a favorite
 
Well, the technician would have to do the scan and there would be a charge for that, you would need at least one radiologist, maybe several, to interpret the findings and there would be charges for that, and your insurance would not pay for anything but the neck. So it would cost you many thousands of dollars for a scan you don't need. And medical resources would be diverted away from patients who do need them. And some radiation exposure as a bonus.
posted by JimN2TAW at 3:16 PM on January 27, 2017


You don't want a full body CT scan unless there's a very good reason.

For one thing, you might want to limit your radiation exposure. (See this article for more on radiation risks.) Also, unnecessary testing increase your risks of being incorrectly diagnosed with an "innocent" problem, which can result in needing potential harmful treatment or further testing. (See this other Scientific American article.)
posted by reren at 3:18 PM on January 27, 2017 [8 favorites]


I think the radiation is one concern, but I am no doctor. I had five chest CT scans (and about 25 chest X-rays) in 2014 and am determined to avoid further where possible. A few links for some background terror!
posted by clone boulevard at 3:18 PM on January 27, 2017


Because a full body scan would subject you to a bunch of unnecessary x-rays.
posted by Bruce H. at 3:19 PM on January 27, 2017


It's the radiation. According to the classic xkcd radiation chart a head CT scan is about 2 msv (millisieverts) of ionizing radiation, and a chest CT scan is 7 msv. A full body scan would therefore be somewhere north of 10 msv of radiation. That's not enough to definitely make you sick, but it's enough that doctors are rightly wary about doing it without a good reason.

For comparison, 1 msv is the amount of radiation that the EPA considers an acceptable annual level of exposure for a member of the public, 4-6 msv is the amount you'd get in a year of just hanging out on planet earth (or about an hour of hanging out on the grounds of the Chernobyl reactor), 50 msv is the annual limit for people who work in jobs that regularly expose them to radiation, and 100 msv in a year is the lowest amount where we have hard data that says "this amount of radiation increases your lifetime risk of cancer".
posted by firechicago at 3:30 PM on January 27, 2017 [3 favorites]


Just to clarify, I kind of figured I'd be exposed to more radiation with a full body. So I'd rather focus on cost and effectiveness/expiration thereof. A full body could be used as a baseline at least 1 or two years down the road right? I'd be willing to pay a couple hundred extra now for that, as opposed to a full grand later when they want to do monthly scans? Just want to get the most money out of irradiating myself I guess.

As far as medical resources being diverted, exactly how does that work? The whole process took ten minutes if that. Would a full body scan really take that much longer? Would I really be stealing resources from someone in need?
posted by one4themoment at 4:04 PM on January 27, 2017


Radiation exposure is a growing concern with CT scans, and I believe that ensuring that they're used judiciously is a burgeoning patient safety measure. Also, doctors aren't really in the business of doing scans and tests just for the hell of it (although in a teaching environment, that may happen to a greater extent). The general rule is don't do a test if the results won't change your plan of care one way or another.
posted by MadamM at 4:06 PM on January 27, 2017 [2 favorites]


As for resources, it's not just the scan but the time of the radiologist who has to interpret it, which does cost money. Was this paid for in part by health insurance? If it's determined by the insurance company that a full body CT wasn't needed given your original reason for having a CT ordered, they may not pay the doctor or hospital. If you just want to pay out of pocket for the doctor and facility time, I guess you could? But it would basically just be for the curiosity of seeing what your insides are like and a tiny chance that you have non-symptomatic cancer.
posted by MadamM at 4:17 PM on January 27, 2017


Doesn't matter if it costs only one cent more. It's not necessary for the problem you're being treated for, so they're not going to order it just to ignore most of it.
posted by kindall at 5:03 PM on January 27, 2017 [2 favorites]


They don't gain you anything except worry and confusion. A detailed scan of a body over the age of 20 is going to show numerous "what-the-fuck-is-that?"'s that will lead to myriad years of follow-up xray's, ultrasounds, and other exams with their inherent cost, worry, and potentially invasive evaluations. The notion that they will somehow show an early cancer is a sensible idea but in practice does not bear out.
posted by docpops at 6:30 PM on January 27, 2017 [5 favorites]


You're much more likely to find something benign that will lead to unnecessary worry/biopsy/surgery/side effects than find a cancer that would otherwise kill you.
posted by chiquitita at 6:33 PM on January 27, 2017 [2 favorites]


Slightly unrelated, perhaps, but maybe more along the lines of what you're looking for -- in evolutionary morphology, we often use Micro-CT scans to image three-dimensional objects like skulls or insect specimens. The machines themselves are extremely expensive, and so we pay for time on the machine, just like we'd pay for time on a SEM scope or a nice confocal microscope with fluorescence. Prices run ~$85-$120 per hour. That's partially overhead and maintenance, and partially to recoup the cost of purchasing the machine. The machines have service contracts, because they are delicate and complex machines that can break down, and so users have to pay so that the service contract can be maintained, too. There's also the salaries of the technicians, the costs of training, etc... Running the machine itself is mostly just the cost of electricity, which is not inconsiderable, but it's really the overhead and maintenance that cost money.

That's in a scientific research setting. In a clinical setting, you also have to balance the time it takes to do a full body scan against the needs of other patients who need scans, too. Every extra minute you're in the machine is a minute it can't be used for someone else.

You can pay to get a full body scan done -- there are places that really specialize in that, much to the chagrin of doctors, who then have to deal with patients with the sort of problems that docpops above is talking about, lots and lots of evidence of potential problems because our bodies are horrific meat puppets that barely work.

On the other hand, my sister, an ob/gyn, used to just give herself ultrasounds all the time when she was pregnant, because she could. I guarantee you if I had a CT machine to myself that I could operate and maintain, I would scan all kindsa shit.
posted by Made of Star Stuff at 8:41 PM on January 27, 2017 [2 favorites]


In addition to what has already been said, there is no single type of scan, whether it's CT, MRI or something else, that can be used to identify or look for all issues (like they do in the movies). Scanning for soft tissue is different than scanning for bone and different than scanning for vasculature and different for scanning organs etc.....

So you would probably have to get multiple full body scans to really look at everything and you're looking at either high cost and/or high radiation exposure and the time and effort of a group of medical people.
posted by eatcake at 8:41 PM on January 27, 2017 [1 favorite]


I know you've said that you know that there would be more radiation involved, but to push home what that means, it's quite likely that a what you are describing would be illegal in the UK inder IRMER (regulations which cover both private healthcare and NHS, so this is purely safety rather than cost). There has to be an expected benefit to the patient which exceeds the danger involved in any exposure to ionising radiation (with an exception for voluntary and informed participation in medical research).
posted by Vortisaur at 3:30 AM on January 28, 2017


I run research grade CT's (not medical, and not on humans).

One other point I don't see mentioned: reconstructing the 3D data from the raw X-ray images takes up a crapload of computer processing time and storage space. The highest res mode I have access to makes 30GB per scan and can take a while to be transferred to someone else's office. As it is, it is likely that the technician cropped the raw data to only the asked-for area when doing the highest-resolution reconstruction (if they wanted the neck, your chin, shoulders, etc are cropped out) and from what I've heard about medical environments, the rest of the data has probably already been deleted.

You may also consider instrument wear and tear (one of my CT's overheats if it runs constantly) and actual time in the room (with setup, cleanup, etc, it may take 30-60 minutes per patient, which limits the number of patients that can be seen per day), the radiologist's time to look through a full body scan and interpret the many small quirks that all human bodies have. Is there a medical question that you think a full body CT would address?
posted by tchemgrrl at 7:34 AM on January 28, 2017 [2 favorites]


I had an abdominal CT recently and thought the same thing: why not get everything once you've got me in the tube?

Aside from radiation dosage and false-positives, the other arguments sound specious to me: Computing time, interpretation time, etc. are all either free these days or could be put off until later until they are free (google AIs doing the work) or worth paying for (other symptoms indicate paying the radiologist).

As a health-care-person myself, having pre-morbid data is so valuable that I can't understand why there isn't a push for this.
posted by soylent00FF00 at 7:10 PM on January 28, 2017 [1 favorite]


37% of whole body scans in aymptomatic patients will have a suspect mass warranting investigation. So lets say you get a CT, and they find a lump. What next?

The vast majority of the time, those lumps will be benign, never cause any problems, and without the scan you'd never know you had the lump

Occasionally the lump will be something that requires treatment

The vast majority of the time it will be the first one

And how do we tell the difference? We have to do a biopsy. Sometimes thats easy, if its a lump close to the skin. But what if its a lump in the kidney or adrenal gland (where the majority of these lumps are), then biopsying this can be risky, cause bleeding, organ damage, and rarely death

So what do we do? Around a third of the time we'll find a lump, and we wont know what the lump is unless we biopsy it. But the majority of the time it wont be anything that needs to be treated, and therefore the biopsy will be an unnecessary risk. Indeed the total harm of biopsies will be greater than the total benefit of diagnosing dangerous cancers, because the lumps found on CT are mostly benign

So what happens when you've had your scan, and they find a lump. Statistically it would do more harm than good to biopsy it. So are you happy to just leave the lump there, or would it cause anxiety and stress that would adversely affect your life?

And if you're not going to do anything about the lump, why bother doing the scan in the first place?

And that's not even mentioning the radiation risk. A whole body CT gives about 17 mSv of radiation exposure, which raises the lifetime risk of fatal cancer by 1 in 1100. That might not sound like much, but in a young asymptomatic person that's less than the likelihood of finding a cancer that requires treatment in the scan. In otherwords its more likely to give you a fatal cancer than find a fatal cancer
posted by DrRotcod at 6:25 AM on January 30, 2017 [2 favorites]


More details: http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm115330.htm
posted by DrRotcod at 6:28 AM on January 30, 2017


Sorry to be a bit of a thread-sitter -- I know we're not supposed to go back and forth and stuff on AskMe, but I feel like this is important to the question and I want to make sure future readers get it.

Computing time, interpretation time, etc. are all either free these days

They're really not. Data storage isn't free, and we're not talking about bitty text files here. Interpretation time sure isn't free. Computer rendering time isn't free, as mentioned by tchemgrll above. Images in particular are the most intensive (rhymes with "expensive") kind of data to deal with in terms of analysis and storage. And if these pre-morbid data are to be of value, then they have to be not only stored but backed up regularly, since the physical medium they're stored on can and will degrade. You can't just write it to a DVD (well, twenty DVDs) and file it. It won't be there in ten years.
posted by Made of Star Stuff at 12:36 PM on February 1, 2017


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