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CT Scan "Reset Error" Gives 206 Patients Radiation Overdose
jeffb (2.718) writes "As the LA Times reports, 206 patients receiving CT scans at Cedar Sinai hospital received up to eight times the X-ray exposure doctors intended. (The FDA alert gives details about the doses involved.) A misunderstanding over an 'embedded default setting' appears to have led to the error, which occurred when the hospital 'began using a new protocol for a specialized type of scan used to diagnose strokes. Doctors believed it would provide them more useful data to analyze disruptions in the flow of blood to brain tissue.' Human-computer interaction classes from the late 1980s onward have pounded home the lesson of the Therac-25, the usability issues of which led to multiple deaths. Will we ever learn enough to make these errors truly uncommittable?"
As long as people are involved in some way, no.
Requiring that doctors RTFM is the first step.
The default setting for an equipment that can be lethal should be "Emit zero radiation". Then for each exposure, set the level of radiation you intend to use. This way, you ALWAYS KNOW the level of radiation the equipment will emit.
Better investigate "Hey, we got no picture" than "Hey, we got pictures, but everyone dies after that..."
Didn't RTFA.
Anyone else read this as David Banner?
Maybe next time they will test the damn thing before subjecting patients to it? It's a built in part of my job that I test/confirm a change after I make a change.. because often there's a likely hood of something unexpected or improperly explained that can cause an issue.
How hard would it have been to stick a dosimeter in the machine after the change and run it though a test?
(I realize that just a basic dosimeter might not be a sufficient measure.. but it would have been good to get a before/after.. and something like a 8-fold increase would have been easily detectable!)
----- The internet has given everyone the ability to have their voice heard equally as loud.. even if they shouldn't be
While the hospital shouldn't have gone and reprogram the instructions, this should have been prevented at hardware level. The machine should register a patient checking in and the amount of radiation emitted.
Will we ever learn enough to make these errors truly uncommittable?"
No.
Along with the usability issues with the design of the Therac-25 it's obvious that the attitude of the medical staff contributed greatly to the problem. Patients complained of being burned, but their complaints were essentially ignored. Meanwhile, they were sent back for multiple treatments. Overwhelming evidence of radiation burns was ignored or given only cursory investigation because medical personal or manufacturer reps claimed that it was impossible for the Therac-25 to be responsible for the burns.
What's a few hundred rem among friends?
*insert pithy sig here*
There is and never will be such a thing as a machine without the possibility for error. And you'll never get around the old adage/rule - If it can happen, it will. How often it occurs it the key; and while we should always aim to make an error-less machine, it is an impossibility and we can only achieve it by make the occurrence of such errors as few and far between as possible.
After all, an error-prone human must be involved to make the machine; even if that machine made another machine a human was still involved at some point to make the original. Thus there will always be the possibility for errors. Even if, as demonstrated by the Matrix, iRobot, and many others, the machines make that error on purpose to save humanity - it is still an error.
Truth is like the sun. You can shut it out for a time, but it ain't goin' away. - Elvis Presley (source: imdb.com)
Would a film badge provide a "check" to determine if the dosage is correct? One x-ray overdose is bad enough, over 200 is really uncool.
Life is brutal, but that doesn't mean we should give up on trying to make it less so. Asking whether CT scanners can be redesigned to make this not happen, and whether it's worthwhile to do so, is very valid.
Will we ever learn enough to make these errors truly uncommittable?"
No. As long as correctness can't be proven and operators are permitted to create unanalyzed conditions by altering protocols there will always be risk. There are probably other mis-configured CT scanners out there in use right now that have been overdosing patients for years.
CT scans use X-rays; an easily detected frequency of light. Why not require that scanners incorporate an independent detector that measures the amount X-ray energy? If that is possible then create an interlock that can shut down the emitter when the net energy gets out of bounds and require that any such incident be NRC reportable. If the detector excluded from alteration by the operators then software bugs, misunderstandings, etc. can be detected even years after the last engineer had contact with the system, either before harm is done or at least before hundreds of patients are literally burned.
Lurking at the bottom of the gravity well, getting old
For patients undergoing scans or treatments involving radiation, why not verify exposure with a 25 cent dosimeter? You'd catch problems right away.
Comment removed based on user account deletion
100s of mSv range
There are portions of the world that have a very high natural background in the 200 mSv range so you are not quite right with your estimates. In addition, you have to distinguish between whole body dose and localized dose. It is not uncommon to see tumor doses in the 40-50 Sv range.
.5 Gy (for xrays 1 Gy = 1 Sv) and got 3-4 Gy. A whole body dose of just above 4 Sv is a 50% death in 3-6 weeks (with no medical intervention). (remember that the CT was only to the brain). They are definitely in some dangerous territory, but the article said the median age of the patients was 70. Couple that with the fact that they already had a stroke and it is safe to conclude that long term effects are unlikely to matter.
The machines were set for
The advantages of simplified training are not just beneficial on an economic scale. While its unfortunate that this error killed people, think of how many more people would die if complex training was required to use these types of machines. Ultimately, it would lead to fewer operators and thus less access to the machine, which ostensibly helps save lives.
Monstar L
Now there are 206 hulks running around.
Just don't make them angry.
In 1895, Thomas Edison investigated materials' ability to fluoresce when exposed to X-rays, and found that calcium tungstate was the most effective substance. Around March 1896, the fluoroscope he developed became the standard for medical X-ray examinations. Nevertheless, Edison dropped X-ray research around 1903 after the death of Clarence Madison Dally, one of his glassblowers. Dally had a habit of testing X-ray tubes on his hands, and acquired a cancer in them so tenacious that both arms were amputated in a futile attempt to save his life.
"Kill 'em all and let Root sort 'em out"
I don't think being trained to fully understand the automobile will decrease the number of automobile related deaths.
Being trained to fully understand the laws of physics would certainly decrease automobile accidents.
This particular error is the kind that occurs when you simplify complex procedures in the interest of widespread use. It is the fault of specialization, which we typically embrace because it allows us to leverage human labor into increasingly complex areas of inquiry. It's more than just "human oversight" or "machine failure," it's the kind of problem that typically arises when people are trained to use machines without being trained to fully understand those machines.
A certain segment of society--that's mostly us geeks--strives against this tendency; we become technicians in various fields. But most people, including medical people, get trained by vendors to use a particular piece of software or hardware without reference to its underlying principles or inner workings. This is normal and usually beneficial for various reasons an economist could doubtless relate.
But one of the things that we geeks should be doing is looking at equipment like this in its overall system context, which includes the operator and which includes the training the operator has received. That's mandatory in the Aviation industry pretty much worldwide (my field); I don't know what the situation is for medical equipment in the USA. No, we will never make such mistakes "uncommittable" -- perfect safety is a myth. But we should be considering possible failure modes, and the likelihood and consequences of those failure modes, to ensure that the risk is tolerable.
Quidnam Latine loqui modo coepi?
"chemo" refers to chemotherapy, where the patient is poisoned in the hopes that the poison will kill the cancer faster than it kills the patient. It is a different form of therapy than radiation therapy, in which the patient is subjected to intense doses of radiation in the hopes that the radiation will kill the cancer faster than it kills the patient. Often, people with cancer will receive both, one after the other, but they aren't the same thing.
The article is not very detailed, but my reading of it is that the default dose was not unsafe. If I am correct (hard to tell), what happened was that a doctor doing a specialized procedure programmed a custom dose. Then the machine defaulted to this new value for subsequent procedures, but the staff assumed it was using it's previous (safe) default.
What is particularly appalling is that it took 18 months to catch this, and they only found out because a patient complained of hair falling out. The FDA recommendation is that doctors double-check that the machine is actually applying the correct dose.
It seems clear to me that this is a stop-gap that indicates a design flaw. It is not enough for the machine to display the actual dose: the procedures for using it must ensure that this is not missed. From the Therac-25 link:
This describes perfectly the recent incident. User-friendly defaults resulted in health professionals making unsafe assumptions. Blaming them does nothing to prevent such problems in the future. The system is broken.
Incidentally, I am not convinced by the lessons learned about Therac-25. It emphasizes proper software engineering practices and licensing. This may be necessary but insufficient.
This might not be enough. Initial testing of the machine had been of hardware only, though the problem was with software. Following the initial reports of an overdose, the company replaced a hardware component. If the real problems fall outside current engineering practices, they may be completely overlooked. In the recent case, the problem appears to include the practices of medical staff. These are part of the technical system, so they need to be treated as such by engineers. Ignoring that is very much like focusing on the hardware to the exclusion of the software. Technical systems are not clearly bounded, and are probably less so as time goes on. There always needs to be a broader view.
Therac-25 suffered suffered (among other things) from race conditions. The mere idea of having a deadly device that is even theoretically susceptible to race conditions terrifies me: if a race condition programming error is even potentially possible, I would want to make damned sure there's an independent hardware or software check to make sure failures will be caught. Problems like this can be incredibly subtle. I wonder if overconfidence in engineering might lead to complacency.
What really jumped out at me, however, was the role of the user community, which was formally excluded from the engineering. Following the discovery of one deadly software error, the company (AECL) fixed it and assumed the problem was solved: after which another patient died from a different bug. The users asked for access to the source code. This was denied. Unlike the company (and likely its engineers), the users clearly understood that they were part of the system.
That pops up for the operator to respond to....
Are you sure you want to kill this patient?
Yes No Retry
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Yes, because we all know that car accidents only kill stupid people...
I don't think the laws of physics cares how high your IQ is when you get t-boned by a drunk driver at an intersection.
Typical normal CT scan dose: 1-2 rem
Faulty CT scan overdose: 8-16 rem
1950s shoe-salesman's fluoroscope: 10 rem
Typical normal Therac-25 dose: 200 rem
Malfunctioning Therac-25 dose: 15-20,000 rem
Come on, seriously people. Yes, this is a mistake that needs to be fixed, but millions of kids in the '50s got their feet nuked with this much radiation and lived to become healthy normal adults with normal feet.
The Therac-25 cooked straight through people, leaving a hole of rotting meat behind. This is not even remotely in the same league.
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/R/Radiation.html
http://chestjournal.chestpubs.org/content/107/1/113.full.pdf
http://www.ccnr.org/fatal_dose.html
http://www.orau.org/ptp/collection/shoefittingfluor/shoe.htm
...But in that particular accident, the drunk is less likely to suffer severe or fatal injuries. The relaxant effect of alcohol makes their body more resilient to sudden shocks. Also, they're usually having a head-on collision, while they may be striking the other vehicle from the side; as head-on collisions are by far the most common, most of a car's safety features are geared toward mitigating them.
Don't you wish your girlfriend was a geek like me?
The person who reacts correctly to a slide is not doing so because he understands physics in general but because he has driving specific training. There's really no time to do math in that situation.
While its unfortunate that this error killed people
There is no mention of any deaths.
Even under normal circumstances, the procedure requires more radiation than most other types of CT scans. Radiation exposure increases the likelihood of cancer, though the risk is lower in older patients because they are likely to die of other causes first.
The median age of these patients is 70 years - and they are surely far more at risk of a second - more dibilitating - stroke than a cancer that might not manifest itself for another five, ten, or fifteen years.
I always thought it was 10% luck, 20% skill, 50% concentrated power of will, 5% pleasure, 50% pain, 100% reason to remember the name.
Conscience is the inner voice which warns us that someone may be looking.
The watchdog timer on the radiation module detects lack of input and shuts it down?
Speak for yourself. I mounted a pad of engineering paper to my dash for just such an occasion. Just this afternoon I was drifting to the left due to rain slick roads, and once I had done the necessary calculations, I realized I ought to depress the throttle 16 mm and turn the steering wheel 68.5 degrees in the +x direction in order to regain control.
Conscience is the inner voice which warns us that someone may be looking.
Was that before or after your car hit the bottom of the ravine?
Check out my sci-fi/humor trilogy at PatriotsBooks.
I don't know. I never have really understood Statistical Mechanics and I have probably not already died in a car accident.
Squirrel!
I don't know about the US, but in the UK the qualification you take to give CT scans these days is usually a degree - you'd be a diagnostic radiographer. How much more training do you want?
The problem isn't the qualification, it's the change in protocol. Someone thought it would be a good idea to override the machine's inbuilt safety cutout by resetting it part-way through the scan, proving that being highly qualified is no barrier to making dangerous decisions.
Woops, silly me, repeating what I learned in upper-division Transportation Engineering lecture from professors with decades of experience in the field of road design. Guess I should have checked Wikipedia first, because it never lies!
Got a cite for your critique?
It's true that the majority of people who die in alcohol-related crashes have a BAC of .08 or higher (67% according to this site). However, lower down, we see that 37% of single-car crashes involve a BAC of .08 or higher, which is higher than the 22% average rate. Since my point was about the comparative risks to the drunk driver and the sober driver in an accident, single-car crashes are irrelevant. That takes out 67% of the drunk driving crashes overall, and similarly lowers the fatality numbers considerably.
Don't you wish your girlfriend was a geek like me?
Only if you accept that it will never be reached, and that there is a tradeoff in aiming for it. I'm all too used to the media and government calling for punishment for those who failed to do what could not be done, or processes getting bogged down with "protections" that will probably never protect in the lifetime of the systems they "protect". Safety is best served by realism and honesty, not by a "something must be done" attitude.
Quidnam Latine loqui modo coepi?
You're saying it's better NOT to find the bug in the code responsible for turning off the X-ray?
Jesus, what must your code look like?
ResidntGeek