Medical Radiation Exposure....

[lutzhoffman]

After some recent medical radiation exposure horror stories, the US government is finally talking about mandating the tracking of medical exposure levels. The case in question resulted from a woman seeing 5 doctors, all of which were ordering CT's. Her bone marrow dose was about 25 rem, that's 25,000 mr, or 5 times the max. permissible yearly dose for radiation workers: This is where they send you home, or give you a desk job after exceeding 5 rem in any year. The current estimate is that in every year there are 10,000 extra cases of cancer and leukaemia etc. in the United States alone, from unnecessary from medical exposure.

The studies on unnecessary patient exposure have shown that 80% of all of this unnecessary patient exposure is from two general exam groups: Abdominal CT's or cat scans, and T-L spine X-rays. If you fall off the roof, or if you suffer some severe trauma, a complete 5 view l-spine x-ray series is still the best diagnostic tool for the job, and indicated. The benefit vs risk ratio is still very favourable in this case. If on the other hand your back just hurts, then you need an MRI, and not an X-ray series. X-rays will show nothing except normal wear and tear, or arthritis. The MRI to boot involves zero radiation exposure, and it shows all of the soft tissues in addition to the bone. Soft tissues are where 90% of the problems are, in non trauma cases. One problem is, that we have a whole generation of MD's, and providers, which went to med. school in the pre-MRI era, and getting many of them to change their diagnostic tools, in order to keep up, has been a real struggle. It is like the old saying of teaching an old dog new tricks. Now throw in the lawyers, and you can double the number of diagnostic exams ordered just for legal reasons. As far as non-MD's like Chiropractors go, I will present one statistic from the boys at the state dept of noise and radiation safety in my state, and let you make up your own mind: When they go inspect, most violations result in no fine, and only a simple written letter of mandated corrective actions from the state. The last year when I asked them, they had issued only 9 actual fines for what were deemed very serious violations. The breakdown was 8 chiropractors, and one dentist.

I do not want to make people paranoid, but in the present climate, it is up to you to track your exposure, and they will give you the numbers if you only just ask. My reason for posting this is because we tend to be so careful at home in the lab, with normally miniscule amounts of exposure, yet we sometimes do not even bother to ask when we have test, after test, ordered by the doctor, or other provider. In a nutshell, extremity X-rays like hands, feet, shoulders, knees, etc. are very low exposure, and the lead apron is not so much for physics, but more for psychological reasons due to an under educated public, I have had patients ask me if we use "uranium" to do their chest X-ray, seriously. Chest X-rays are so miniscule in exposure, that they can be done on a pregnant woman safely, for the average size male you will get about 50-80 mr. The exams to watch out for are: Abdominal CT's, and lower back X-rays, and fluoroscopy. Angio heart cath procedures can be very high also, in these cases a single exam can be between 1.5 - 5 rem, or 1,500-5000mr, which is very substantial, when compared to a chest at about 50-80mr. The new unit of measurement is sv, so to convert: one centi sv = about 1 rem, or 1000mr.

Also ask about the operating room, they can fluoroscope you there, and you will not know a thing, since you are under. This can be up to 5,000-10,000 mr in some complex hip operations. Last year a few patients in the US actually had X-ray skin burns, from fluoro, and angio procedures, these are the ones that were reported, who knows how many others occurred. I was also surprised to learn that most nuclear medicine procedures where you get injected with a radioactive isotope in the several mCi level range on average, are not that bad, maybe due to the short half lives of the isotopes used .So do not be afraid, but just ask, if you are concerned. The moral is don't be shy, and make sure the answer is a number, and not an analogy : )

[Doug Coulter]

And we didn't even have to mention the Therac-25 (oops, said it again -- Monty Python). I find it interesting that our government is so self-confused that at the same time they are talking about raising permitted exposure levels -- and doing this. Which is also discussed on Schneier's forum. Of course there they are discussing other implications of warrant-less searching techniques -- it's specialized on aspects of security there.

I know this -- I have to be a near-goner before I ever let that gas-passer near me, they tend to OD me and that's life threatening on its own. I can take the pain without that usually anyway, and I find that this makes the guys inflicting it a lot more careful -- less total pain later from incidental damage they do to a piece of meat, rather than to an awake person. I find being conscious makes them work harder to get it right on the first try -- and really disturbs the ones who can't take that extra pressure of me looking them in the eyes while they do it.

I was recently in the hospital over a bunch of broken ribs (ow!). They wanted me "out" but I refused. After half an hour taking X rays of the wrong side of my body, I spoke up and said something like "Doc, I have this enormous diagnostic advantage over you here". He mulls for a second and says "what is it?". "I'm connected to the nerves that are screaming!" "Oh". Seems there was some mis communication between the EMTs and the emergency room on which side was hurt -- they were working me from the back (where they broke) and the hospital was looking at the front...
I thought they had some fancy terminology for sorting that out, but they evidently didn't get it right that time, and were clueless even after looking at the X rays of the wrong side and seeing no damage there (duh). Actually, they had trouble with that on the correct side. A "healer" was on a ride-along with the EMT's and she had reset the ribs right on the spot with her fingertips so well there wasn't much to see anyway, but I can tell you, from the inside that made the difference between a dying man who didn't care much and a guy wanting to jump and shout (in pain, but still better ).

I note that more modern plain X ray equipment is getting to be pretty sensitive, and knowing some little about it, I look at the meters to check if they are using that, or some dinosaur that is very high dose -- I check that mA meter real closely, and of course, you can hear the thing expose (they all click and hum) so you get a take on "how long". Of course, long term things like CT are a lot worse, as the exposure integrates over the long time. They could improve that if the guys writing the software knew more signal processing math, sigh. The brute force technique most of the CT scanners use needs a lot more dose to get a good picture than what is possible to do with better algorithms.

Of course, doctors and "safe" can get humerous indeed. I have a bunch of "cerro shield" they used to use because it's safe -- low melt point. But it's full of cadmium! Some new meaning of the word "safe"? But considering that my Mom, a psychologist who only talked to people (no drugs or procedures) was paying nearly $35/hour for malpractice insurance back in the last century, well....not all the dangers are medical, as Lutz points out.

[lutzhoffman]

Some further notes, and a good link:

If you have chronic back pain, and your doc insists that he needs X-rays, then you can request that a limited series be done, this is 2-3 views instead of the normal 5+ with half of the exposure, and it will give the same end diagnostic result, at a lower price if you have to pay. Now your doc. can relax since his perceived legal monkey, is now off his back with the x-ray done, and now he can order the MRI.

For many conditions there are also zero exposure alternatives, like MRI, ultrasound, etc. which is real nice for women and for the breast. If I were female: I would NEVER do yearly mammograms, unless I had a legitimate risk factor like a family history etc. One every couple years is enough for most women, research this one youself, it is worth your time to do so. Just a little under 1% of women carry a gene making them highly sensitive to radiation induced breast cancer, they are currently working on a test, for this nasty gene, but nothing yet to date. For this small percentage of women, a mammogram is a really bad idea. On this subject infrared thermography, which is used by some quack naturopathic, and chiropractic, "witch doctors": Thermography does not find cancer, and it has been positively shown in recent studies to be useless.

I had to chuckle while reading Doug’s comments about the rib situation, this is a perfect example of silly providers, and maybe even hospital money / profit motives: First, there is no treatment for rib fractures period, so what's the point of ordering the rib x-rays? It will not change the treatment, or the final outcome, which is normally limited to ibuprofen, or hydrocodone for the pain, so that the unfortunate person can sleep. In some rare instances the offending displaced rib can be pushed from the outside to obtain relief, but this comes with the risk for a puntured lung etc, so still better then to do a simple lower exposure chest x-ray afterwards, since the original problem is very obvious from the outside, just by using the "optical imaging" system. Non displaced rib fractures on x-rays are almost impossible to spot on anyone who is not an anorexic woman, since the image contrast is so poor, due to having to penetrate the entire chest cavity. The normal lung markings also tend to obscure all of the fine detail. The smarter docs will just order a chest x-ray instead of a rib series, if they feel they have to document things for some reason, because it will show any displaced rib fractures just as well, and it will rule out any lung problems from the trauma to boot. The kicker is that a chest x-ray is about 10- 20% of the radiation exposure of a rib series, since you turn the penetration up from 74-80KV, to about 120KV for the chest x-ray, thus requiring far less total radiation, most of which is absorbed, and wasted in the body at 74-80KV. The "theory" in the rib series is to boost the bone contrast by lowering the KV to about 74 - 85KV, in reality any advantage tends to be eaten up by the lung markings, and by other superimposed features also becoming more prominent. The x-ray technologist also screwed up, because he did not ask the best expert where the pain is, which was Doug, duhhhh, this IS part of their scope of practice and part of their job. The original rib series order from the doc, is also a prime example of medical "autopilot" where folks do not think about what they are doing, in a systematic logical way. One other sad note is that the average MD does not even have a clue, on how much exposure is involved with a given exam. Thus you cannot count on the MD to protect you in a radiobiological sense.

Even with the MD radiologists, only a select few have committed even common exposure levels, to memory. This is however the person to ask if you want a real number, instead of some stupid ignorant analogy, like: "Oh its just like a few hours in the sun" which is utter complete bullshit, unless God has just sucked away almost the entire atmosphere, right after a divine solar flare. These MD's can however look it up for you, since they at least know where the book is.

As far as equipment goes, its the receptor system which matters, either CR, DR, or another dig. sytem is fine, with 1/2 of the film exposure. Here is a dirty little secret: Digital plates can be way overexposed with zero loss of detail, so some under educated Rt's who somehow passed the registry, often have been seen turning up the juice a few notches, this way they are assured of not having to repeat the exam, or view which can be a hassle. Most digital units hide a small number on the bottom of the image, which is labled "Exposure Index". With CR It should be between 1400 to 2000. This is a log scale number so if I were to set the machine for 10 times the needed dose, then the image would be fine, but the Exp. Index would read about "2600". I tried this on a phantom after seeing a 2550 reading on one patients exam, this turned out to be 5-8 times what was needed. Also all of the new state of the art machines feature photo-timing via an ion chamber in the table of chest board, which controls the x-ray amount automatically. The problem is when the tech forgets to select "wall", and leaves it set on "table", now you better hope that the backup time is not set to high, or at least a half a second+ will go by, before the tech goes oh shit, and takes his/her finger off the button. Now imagine a chest setting at 120KV at 500ma, that would be 250 milliampere seconds at 120KV, where only 5-15 may be required, if it is set right. With an old machine this is far less likely, this is one reason why I prefer an old trusty machine with a manual setting. The x-ray source can be an old fashioned 60Hz humming machine, as long as the receptor is digital, all will be fine. If on the other hand it is a modern HF one, then you will not hear the massive hum if the tech is tired, hung over etc. and selects table instead of wall.

The best advice if you have the luxury of time, is to just look up the exposure levels on the net. Once you have the exam, then you can search under the various procedures. Below is a primer, for digital x-rays its very close to my figures from the health physicist, but on CT's it seems a bit optimistic, and on the low side, the spine figure is for a thin C-spine, an L-spine for example, would be about 5 times higher in reality. Keep in mind overall body weight is a major factor, when you double the part thickness, then you basically square the dose, so being fat carries a huge exposure penalty. Some exposure tables cheat by using a 120 pound male as the test subject, come on, that was so many big macs, and twinkies ago:

http://www.radiologyinfo.org/en/safety/ ... =sfty_xray

[Bill Fain]

Hi, Does the backscatter x-ray system (Doug's post had a link to it) show up a radiologically "hot" source as a blurry white thing on the screen as I think a regular x-ray does? If so, If I'm driving around DC with a setting of antique fiesta ware in my car, am I going to get stopped by the federalies? If I had it in a lead bag, would they stop me because they couldn't see everything? Doug, should my post stay here or go the "watercooler" section? -bill

[lutzhoffman]

Bill has a valid point here, from a physics perspective x-rays, or gamma photons which are scattered for any reason, always have a lower energy than the primary beam, thus for a backscatter system to work, it would have to pick up a very broad spectrum of x-rays, with little or no descrimination. Thus it will pick up any source of low energy gammas, the same as x-rays. So in a nutshell fiestaware may show up due to the low energy gammas, but probably not to brightly, the lead bag would work fine to hide any hot material if the lead is thick enough to stop the rad. from the source. If the numbers are correct and this system delivers the MPD (Maximum Perm. Dose) in 6 hr of exposure then the dose rate could be either 5000mr/6hr, or 1200mr /6hr depending on which number they are picking ref. to perm. public exposure. Either way it is not good, and only a question of how bad.

There must also be two different energy level systems out there: One with very low dose soft x-rays like at the airport scanners, and one with a much harder beam for thicker stuff like the car. Since the low energy backscatter airport systems cannot penetrate even thin sheet metal, or much below the skin, this system would not be able to image anything like a car. In the example photo the car door, and the stuff inside, even the full bottles, have been completely penetrated. This would require at least 150KV, with 250-400KV being more probable, based on the contrast levels etc. If this is indeed the case, then this needs to be stopped before it proliferates society. This technology could even then be abused to eliminate undesirable individuals etc, if for example they were placed under "observation" a lot, with a high energy system and no time controls. If the former figure is correct, then in a 24hr period up to 20,000 mr could be administered, at this dose 8-10% of the folks would be dead from leukemia or cancer in the following 5- 10 years. To acheive a 20-80mr/hr dose rate at even 2-4 meters the radiation source, if not electronic, would have to consist of at least multi Ci amounts of Ir 192 for example, which is the same turning on an industrial radiography source on the sidewalk ! I can already see how this one will go, geiger counters will become popular, and then they will use a neutron back scatter system instead.

If they ever get one of these airport ones here I am going to time a Tc99m nuc med bone scan with a plane trip, then they will see my full skeleton, instead of the normal external image, I bet that this would mess with the minds of the likely ignorant people that they will have running it, especially if I prime them with a question like: "Sir /Madam: I have very sensitive bones which ache on sunny days, because I am a vampire, will this hurt me like sunlight? and then come out of the machine like I am in considerable pain, commenting that this was even worse than garlic

[Doug Coulter]

FWIW, the airport full body scans coming into use are terahertz RF, not X ray -- no harm we know of, just microwaves and not much power (as it's hard to make THz at all -- it's a gray area where semiconductors don't work well, just below IR energy & frequency). They are phasing out the X ray ones for all the reasons we know -- the "think of the children/pregnant women" meme used to justify otherwise intrusive behavior by those in power. They still use X rays for non-human things (your bags etc) but those are conventional, and fairly low dose as they can get to both sides of the object and do it the normal way that's more efficient.

Backscatter X rays need one heck of a lot more dose than through-the-body to work -- not that big a fraction of what goes out bounces back to image with. We've even accidentally measured that here with gammas from the fusor by putting a big shield between it and a counter -- we then see it bouncing off the ceiling and such like, not so much, but it's there enough to be way over background. So unless they are using ultra sensitive imaging, they've got to be putting out a real dose there (no matter what they say for PR) -- maybe not super high volts, but a lotta current. For that you want X rays that hit the normal K,L lines the "subject" atoms have, and can't count on things like lead and tungsten targets -- you use softer ones that bounce better off the stuff humans are made of, but you need a lot of them regardless. Could be though, that they simply emit high energy and let Compton scattering etc bring them down in energy (in the subject). They didn't say. Security and trade secret stuff.

One wonders if the ban on owning Geiger counters in NY has any relation....Too tinfoil hatty?

I don't think I'd drive around with anything questionable in places this is likely to be used. Let someone else sort out the search/seizure laws first. I think in this atmosphere of government-created fear, you lose.

I don't think anything the looks like it's hiding something helps -- makes it worse, probably. I know what a prosecutor would do with that -- you couldn't pretend ignorance at all in such a case.
It would just give them an excuse to look closer.

At any rate, for other reasons (like once being the subject of what I thought was an utterly unjustified total search at a registration-check traffic stop) I quit having *anything* more questionable in my vehicles than a beer a long time ago. They really tore up a brand new car looking for things that weren't there....and of course, no recourse for me for what it cost to essentially replace all the upholstery they tore to pieces -- heck, I had to pay for them impounding the car!